Is magnesium glycinate the same as taking glycine?

Partly, and this is the thing most people searching this question get wrong. Magnesium glycinate is a magnesium ion chelated to glycine, so taking it means you are already taking both compounds. You are not choosing between them. What you are not getting is glycine's studied sleep dose. The glycinate capsule is dosed by elemental magnesium, 200 to 400 mg in the standard sleep protocol. Glycine's own protocol is 3 g of powder 30 to 60 minutes before bed. If you want that, you add powder on top.

Which is better for sleep, glycine or magnesium?

Neither, statistically. Glycine's sleep-quality subrating is 8.5 and magnesium's is 8.6, a 0.1 gap that decides nothing. Mah 2021 found sleep onset latency 17.36 minutes shorter in older adults on magnesium. Kawai 2015 shows glycine lowers core body temperature through NMDA receptors in the suprachiasmatic nucleus, and Bannai 2012 supports the sleep-quality claim. Different routes, similar destination. Running both costs under $23 a month.

Why does magnesium score higher overall if sleep is a tie?

Breadth. Magnesium scores 8.7 with High evidence confidence against glycine's 7.9 with Moderate, and the gap comes entirely from use cases that have nothing to do with sleep. Magnesium wins cardiovascular 8.0 to 5.8, blood sugar 7.6 to 6.2, mood 7.6 to 6.5 and acute pain 6.6 to 5.0. Each of those rows has a pooled analysis behind it. Glycine's equivalent rows rest on the Soh 2024 systematic review, which covered 50 studies and still concluded that larger well-controlled RCTs are needed.

Does glycine beat magnesium at anything?

One row outright: recovery and repair, 7.5 against 7.0. Glycine is a structural residue in collagen, so it feeds tissue repair as substrate rather than as a signal. Li 2018 covers the collagen biology and de Paz-Lugo 2018 found higher collagen synthesis by articular chondrocytes in vitro. Bone-joint and mitochondrial are honest ties. Everything cardiometabolic goes to magnesium.

How much does each cost per month?

Bulk glycine powder is $20 to $30 a kilo, and a 3 g nightly dose is 90 g a month, so $1.80 to $2.70. Magnesium glycinate at 400 mg elemental is $10 to $20 a month. Both were priced 2026-09-07 through retail channels. The gap is roughly $7 to $18 a month, which is not enough to decide anything. Threonate for cognition costs more, $30 to $45.

How long before I know if either one is working?

Different timescales, and mixing them up is the common mistake. Glycine gives a first noticeable effect in about a day and its assessment window is 2 weeks, so five to seven nights at 3 g tells you most of what you need for sleep. Full effect on connective tissue and glutathione takes about 12 weeks. Magnesium's first noticeable effect is about 3 days, but its assessment window is 8 weeks and full effect is also 8 weeks. Every cardiometabolic endpoint here was measured over that long or longer. Judging magnesium at 2 weeks tells you almost nothing.

Can I take glycine and magnesium together?

Yes, and the glycinate form means most people already do. The magnesium report's own sleep protocol names glycine at 3 g as a stacking partner. The mechanisms are complementary rather than redundant: glycine drops core body temperature and acts as an NMDA co-agonist, magnesium blocks the NMDA pore and modulates GABA tone. Raise one at a time. Both can loosen stools at higher doses, and glycine can cause vivid dreams or morning grogginess if the bedtime dose goes too high, so simultaneous changes leave you guessing which did it.

Who should avoid these?

Kidney disease is the shared exclusion. Magnesium needs nephrology oversight below an eGFR of 30, and glycine's list names complex or advanced kidney disease. Beyond that the lists barely overlap. Glycine is out with primary hyperoxaluria, recurrent calcium oxalate stones, clozapine therapy, and pregnancy or nursing without clinician guidance. Magnesium is out with bowel obstruction, myasthenia gravis or heart block, and needs a 2 to 3 hour gap from bisphosphonates, tetracyclines and fluoroquinolones.

Which magnesium form should I buy if I want the glycine too?

Glycinate, also sold as bisglycinate. It is the best-tolerated form, has a neutral effect on the gut, and is the only common form that delivers glycine alongside the mineral. Threonate is for cognitive goals, malate for daytime energy, citrate for general use with a mild laxative effect. Compare elemental magnesium on the label, not compound weight: 1,000 mg of threonate is only 144 mg elemental.

Head-to-Head Comparison

Glycine vs Magnesium: Which Is Better for Sleep?

Should I take glycine or magnesium glycinate for sleep?

Reviewed 09/08/2026

Magnesium glycinate is magnesium bound to glycine, so if you take it you already take both. That kills the question for sleep. The real decision: magnesium scores higher and wins cardiovascular, mood, blood sugar and migraine rows. Glycine wins collagen repair, and glycinate capsules are dosed for magnesium, not for glycine.

Magnesium glycinate is a magnesium ion chelated to two glycine molecules. Taking it is not choosing between these two.
Sleep quality is a statistical tie: glycine 8.5, magnesium 8.6. The gap is 0.1 and it decides nothing.
Overall, magnesium 8.7 with High evidence confidence against glycine 7.9 with Moderate. That gap is real, and it comes from breadth, not from sleep.
Magnesium wins every cardiometabolic row: cardiovascular 8.0 against 5.8, blood sugar 7.6 against 6.2, mood 7.6 against 6.5.
Glycine wins one row outright, recovery and repair at 7.5 against 7.0, because it is a structural residue in collagen.
The glycinate capsule is dosed by elemental magnesium, 200 to 400 mg. Glycine's own sleep protocol is 3 g of powder. Those are different amounts of glycine.
Cost is not a tiebreaker. Bulk glycine is $1.80 to $2.70 a month at 3 g nightly. Magnesium glycinate is $10 to $20 a month. Both priced 2026-09-07.
Kidney disease is the one exclusion that hits both. Everything else on each list is specific to that side.

At a Glance

Head-to-Head Verdict

Use Case	Winner	Rationale
Sleep Quality	Tie	Glycine 8.5, magnesium 8.6. A 0.1 gap is noise, and the framing is wrong anyway: magnesium glycinate is magnesium chelated to glycine, so anyone taking it nightly already gets both molecules. Mah 2021 found sleep onset latency 17.36 minutes shorter in older adults. Kawai 2015 shows glycine drops core body temperature through NMDA receptors in the suprachiasmatic nucleus. Two routes, one row.
Recovery Repair	Glycine	Glycine 7.5 against magnesium 7.0, the one row glycine wins outright. Glycine is a structural residue in collagen, covered by Li 2018 and by de Paz-Lugo 2018, which found higher collagen synthesis by articular chondrocytes in vitro. Holecek 2025 frames glycine as conditionally essential: synthesis may not cover demand. Magnesium's score rests on general physiology, not a repair endpoint.
Cardiovascular	Magnesium	Magnesium 8.0 against glycine 5.8, the widest gap here, and it separates pooled outcomes from a plausible mechanism. Argeros 2025 pooled 38 RCTs and 2,709 people: systolic pressure fell 2.81 mmHg overall, 7.68 mmHg in treated hypertensives. Zhang 2016 pooled 34 RCTs for 2.00 mmHg. Glycine has one blood-pressure trial, Diaz-Flores 2013 at 5 g a day, and only in metabolic syndrome.
Blood Sugar	Magnesium	Magnesium 7.6 against glycine 6.2. Asbaghi 2022 found HbA1c 0.73% lower at 500 mg a day in type 2 diabetes, and Fang 2016 found 36% lower risk at the highest dietary intake quintile. Glycine's case is thinner: Tan 2025 was a single-arm study of 19 people with severe obesity that moved selected markers but not body weight, insulin resistance or glutathione. That is a signal, not a result.
Mood	Magnesium	Magnesium 7.6 against glycine 6.5. Tarleton 2017 was an open-label randomized trial in 126 adults reporting PHQ-9 down 6.0 and GAD-7 down 4.5 in two weeks, NNT around 3. Open-label is a real limitation, which is why magnesium sits at 7.6 and not higher. Glycine has no depression trial at all. Its 6.5 comes from the nervous-system signal in Soh 2024, a review of 50 studies.
Acute Pain	Magnesium	Magnesium 6.6 against glycine 5.0, and one endpoint carries it: migraine. Chiu 2016 pooled intravenous and oral magnesium for a migraine frequency odds ratio of 0.20. The protocol is 300 to 600 mg elemental daily for a minimum of 8 weeks before you judge frequency. Glycine has no pain trial at all, so its 5.0 is a mechanism-only score. That is what one should look like.
Bone Joint	Tie	Both score 7.0, and the tie is honest because they build different parts of the same tissue. Bone holds roughly 60% of total body magnesium as a long-term reservoir (de Baaij 2015). Glycine is a collagen residue, the organic scaffold that mineral sits in (Li 2018, de Paz-Lugo 2018). Neither has a fracture outcome trial. Take both, and glycinate delivers both in one capsule.
Mitochondrial	Tie	Magnesium 7.6 against glycine 7.2, and the 0.4 gap does not survive a look. Magnesium's case is structural: ATP circulates as an ATP-Mg complex (de Baaij 2015). Glycine's runs through glutathione, and the cleanest test was mixed. Gut 2021, in 114 older volunteers, found the primary glutathione endpoint unchanged. Kumar 2023 tested glycine plus NAC together, not glycine alone. Call this row even.

Cost Comparison

Intervention	Monthly Cost	Notes
Glycine	$1.80 to $2.70	Priced 2026-09-07, retail channel, at the 3 g oral sleep dose. Bulk pharma-grade glycine powder runs $20 to $30 a kilo, and 3 g a night is 90 g a month, which lands the monthly cost under $3.Capsules cost several times more per gram, because a 3 g dose is 3 to 6 capsules. The form drives almost the entire price difference here, not the brand. If you are taking multi-gram doses, powder is the rational purchase.
Magnesium	$10 to $20	Priced 2026-09-07, retail channel, at 200 to 400 mg elemental magnesium as glycinate. The $10 to $20 range is quoted at 400 mg a day, the top of that protocol's range, so a 200 mg dose sits at the low end.Form changes the number substantially. Threonate for the cognitive niche runs $30 to $45 a month and ionic forms $25 to $35. Oxide is nearly free and poorly absorbed, which is the trap. Compare elemental magnesium, never compound weight.
The difference	About $7 to $18 a month	Subtract the ranges and glycinate costs roughly $7 to $18 a month more than bulk glycine powder. Over a year that is under $220 at the worst end. This is the wrong place to optimize.Running both is the interesting number: under $23 a month at the top of both ranges. Given that the two mechanisms are separate and the sleep subratings are within 0.1 of each other, buying both costs less than most single sleep supplements and removes the question entirely.

When to Switch

Nothing here needs switching, because these two overlap by design. Magnesium glycinate is magnesium chelated to glycine, so the default move is to run both rather than choose. What changes is the dose of each.

Judge glycine fast. Its first noticeable effect lands in about a day and the assessment window is 2 weeks, so five to seven nights at 3 g pre-bed tells you most of what you need for sleep. Full effect on the slower endpoints, connective tissue and glutathione, is around 12 weeks.

Judge magnesium slowly. First noticeable is about 3 days, but the assessment window is 8 weeks and full effect is also 8 weeks. Every cardiometabolic endpoint in this comparison was measured on that timescale or longer. A 2-week magnesium verdict is not a verdict.

Add glycine powder on top of glycinate when sleep onset is still the complaint after a full magnesium window. The glycinate capsule is dosed by its elemental magnesium content, not to hit glycine's 3 g sleep protocol.

Add or raise magnesium when the target moves to blood pressure, glucose, migraine frequency or mood, where glycine has no trial evidence. Drop back to glycine alone if magnesium gives you loose stools you cannot titrate around, though glycinate is the best-tolerated form and switching off citrate or oxide usually fixes that.

Two hard limits on the stack. Glycine can also loosen stools and produce vivid dreams or morning grogginess if you push the bedtime dose too high, so raise one thing at a time or you will not know which one did it. And magnesium needs a 2 to 3 hour gap from bisphosphonates, tetracyclines and fluoroquinolones, which is a timing rule glycine does not impose.

Who Should Pick What?

Already taking magnesium glycinate and wondering whether to add glycine

Glycine

Add it, and stop thinking of this as a choice. Your capsule is dosed by elemental magnesium, 200 to 400 mg, not to deliver glycine's 3 g sleep protocol. Bulk glycine powder costs $1.80 to $2.70 a month at that dose. Give it five to seven nights and you will know.

Adult with high blood pressure or a family history of it

Magnesium

Magnesium's cardiovascular subrating is 8.0 against glycine's 5.8, and Argeros 2025 pooled 38 RCTs for a 2.81 mmHg systolic drop overall, 7.68 mmHg in people already on treatment. Glycine has nothing comparable at the blood-pressure endpoint. Give it 8 weeks and track the number.

Vegan, vegetarian or on a low-collagen diet

Glycine

The glycine report puts this group at the top of its likely-upside list, alongside older adults and high-methionine diets. Holecek 2025 treats glycine as conditionally essential, meaning endogenous synthesis may not cover demand. Recovery and repair is the one row glycine wins outright, 7.5 against 7.0.

Gets migraines

Magnesium

Chiu 2016 reported a migraine frequency odds ratio of 0.20 across intravenous and oral magnesium trials. The protocol is 300 to 600 mg elemental daily, split twice, for a minimum of 8 weeks before you judge frequency. Glycine has no pain or migraine evidence in its set at all.

Type 2 diabetic or watching a rising HbA1c

Magnesium

Blood sugar 7.6 against 6.2. Asbaghi 2022 found HbA1c 0.73% lower at 500 mg a day in type 2 diabetes, and Fang 2016 found 36% lower risk at the highest dietary intake quintile. Glycine's glucose data is a single-arm study of 19 people that did not move insulin resistance.

Takes a PPI, trains hard, or is over 65

Magnesium

Roughly 50% of US adults fall below the magnesium RDA per NHANES, and the report names PPI users, athletes, vegetarians, the elderly, type 2 diabetics and post-bariatric patients as running lower still. Correcting a real deficiency is a better use of the first $20 than anything else in this comparison.

Has advanced kidney disease or a history of oxalate stones

Tie

Neither, without a clinician. Kidney disease is the one exclusion both sides share: magnesium is contraindicated below an eGFR of 30 without nephrology oversight, and glycine's list names complex or advanced kidney disease. Recurrent calcium oxalate stones and primary hyperoxaluria rule out glycine specifically.

Taking clozapine or another antipsychotic

Magnesium

Glycine is the wrong side here. Evins 2000 found glycine added to clozapine produced no significant symptom or cognitive improvement, and glycine's contraindication list names clozapine therapy and psychiatric medication without clinician input. Magnesium carries no antipsychotic interaction, though drug timing rules still apply.

Research Highlights

Form Overlap
Magnesium glycinate is magnesium chelated to glycine. Anyone taking it for sleep is already taking both compounds in this comparison, which is why the sleep-quality subratings sit 0.1 apart at glycine 8.5 and magnesium 8.6. The question people search for does not have two sides.What does have two sides is dose. A glycinate capsule is dosed by its elemental magnesium content, 200 to 400 mg in the standard sleep protocol. Glycine's own clinical sleep protocol is 3 g of powder taken 30 to 60 minutes before bed. Those are not the same amount of glycine.
Mechanism Difference
These two are complementary, not redundant, and they meet at one receptor. Glycine is an inhibitory neurotransmitter and an NMDA co-agonist that drops core body temperature through peripheral vasodilation, which is what speeds sleep onset. It separately supplies rate-limiting substrate for glutathione and collagen synthesis.Magnesium sits in the NMDA receptor pore as a voltage-dependent block, modulates GABA tone, and relaxes vasculature by antagonizing calcium entry. It is also a cofactor for hundreds of enzymes and circulates bound to ATP. One is a substrate and a signal. The other is a structural cofactor. They touch the same receptor from opposite directions.
Safety Comparison
Both sit near the floor on risk. Glycine scores 1.3 on safety risk and 1.3 on side effects, magnesium 1.2 and 1.3. Neither has a worst-case story worth leading with in a healthy adult. The exclusions are what matter, and they barely overlap.Glycine is out with primary hyperoxaluria, recurrent calcium oxalate stones or clozapine therapy. Magnesium is out with bowel obstruction, myasthenia gravis, heart block, and needs a 2 to 3 hour gap from bisphosphonates, tetracyclines and fluoroquinolones. Kidney disease excludes both: below an eGFR of 30 for magnesium, complex or advanced disease for glycine.
Cost Comparison
Bulk glycine powder runs $20 to $30 a kilo, so a 3 g nightly dose is 90 g a month and costs $1.80 to $2.70. Magnesium glycinate at 400 mg elemental runs $10 to $20 a month. Both figures were priced 2026-09-07 through retail channels.That makes the gap roughly $7 to $18 a month, which is too small to decide anything. Running both costs under $23 a month at the top of both ranges. Form is where the money actually moves: glycine capsules cost several times more per gram than powder, and magnesium threonate runs $30 to $45.
Editorial Verdict
Magnesium scores 8.7 with High evidence confidence against glycine's 7.9 with Moderate, and that gap is earned on breadth rather than on sleep. It wins cardiovascular 8.0 to 5.8, blood sugar 7.6 to 6.2, mood 7.6 to 6.5 and acute pain 6.6 to 5.0, each anchored to a pooled analysis glycine has no answer for.Glycine wins recovery and repair, 7.5 to 7.0, on its collagen substrate role, and ties bone-joint and mitochondrial. If sleep is the only goal, the honest answer is that magnesium glycinate already contains both, and the only upgrade left is adding enough glycine powder to reach the 3 g dose.

Frequently Asked Questions

Is magnesium glycinate the same as taking glycine?: Partly, and this is the thing most people searching this question get wrong. Magnesium glycinate is a magnesium ion chelated to glycine, so taking it means you are already taking both compounds. You are not choosing between them.What you are not getting is glycine's studied sleep dose. The glycinate capsule is dosed by elemental magnesium, 200 to 400 mg in the standard sleep protocol. Glycine's own protocol is 3 g of powder 30 to 60 minutes before bed. If you want that, you add powder on top.
Which is better for sleep, glycine or magnesium?: Neither, statistically. Glycine's sleep-quality subrating is 8.5 and magnesium's is 8.6, a 0.1 gap that decides nothing. Mah 2021 found sleep onset latency 17.36 minutes shorter in older adults on magnesium.Kawai 2015 shows glycine lowers core body temperature through NMDA receptors in the suprachiasmatic nucleus, and Bannai 2012 supports the sleep-quality claim. Different routes, similar destination. Running both costs under $23 a month.
Why does magnesium score higher overall if sleep is a tie?: Breadth. Magnesium scores 8.7 with High evidence confidence against glycine's 7.9 with Moderate, and the gap comes entirely from use cases that have nothing to do with sleep. Magnesium wins cardiovascular 8.0 to 5.8, blood sugar 7.6 to 6.2, mood 7.6 to 6.5 and acute pain 6.6 to 5.0.Each of those rows has a pooled analysis behind it. Glycine's equivalent rows rest on the Soh 2024 systematic review, which covered 50 studies and still concluded that larger well-controlled RCTs are needed.
Does glycine beat magnesium at anything?: One row outright: recovery and repair, 7.5 against 7.0. Glycine is a structural residue in collagen, so it feeds tissue repair as substrate rather than as a signal. Li 2018 covers the collagen biology and de Paz-Lugo 2018 found higher collagen synthesis by articular chondrocytes in vitro. Bone-joint and mitochondrial are honest ties. Everything cardiometabolic goes to magnesium.
How much does each cost per month?: Bulk glycine powder is $20 to $30 a kilo, and a 3 g nightly dose is 90 g a month, so $1.80 to $2.70. Magnesium glycinate at 400 mg elemental is $10 to $20 a month. Both were priced 2026-09-07 through retail channels. The gap is roughly $7 to $18 a month, which is not enough to decide anything. Threonate for cognition costs more, $30 to $45.
How long before I know if either one is working?: Different timescales, and mixing them up is the common mistake. Glycine gives a first noticeable effect in about a day and its assessment window is 2 weeks, so five to seven nights at 3 g tells you most of what you need for sleep. Full effect on connective tissue and glutathione takes about 12 weeks.Magnesium's first noticeable effect is about 3 days, but its assessment window is 8 weeks and full effect is also 8 weeks. Every cardiometabolic endpoint here was measured over that long or longer. Judging magnesium at 2 weeks tells you almost nothing.
Can I take glycine and magnesium together?: Yes, and the glycinate form means most people already do. The magnesium report's own sleep protocol names glycine at 3 g as a stacking partner. The mechanisms are complementary rather than redundant: glycine drops core body temperature and acts as an NMDA co-agonist, magnesium blocks the NMDA pore and modulates GABA tone.Raise one at a time. Both can loosen stools at higher doses, and glycine can cause vivid dreams or morning grogginess if the bedtime dose goes too high, so simultaneous changes leave you guessing which did it.
Who should avoid these?: Kidney disease is the shared exclusion. Magnesium needs nephrology oversight below an eGFR of 30, and glycine's list names complex or advanced kidney disease. Beyond that the lists barely overlap.Glycine is out with primary hyperoxaluria, recurrent calcium oxalate stones, clozapine therapy, and pregnancy or nursing without clinician guidance. Magnesium is out with bowel obstruction, myasthenia gravis or heart block, and needs a 2 to 3 hour gap from bisphosphonates, tetracyclines and fluoroquinolones.
Which magnesium form should I buy if I want the glycine too?: Glycinate, also sold as bisglycinate. It is the best-tolerated form, has a neutral effect on the gut, and is the only common form that delivers glycine alongside the mineral. Threonate is for cognitive goals, malate for daytime energy, citrate for general use with a mild laxative effect. Compare elemental magnesium on the label, not compound weight: 1,000 mg of threonate is only 144 mg elemental.

Evidence Sources

Meta-analysis Magnesium supplementation and blood pressure: updated meta-analysis (2025) 38 RCTs and 2,709 participants. Systolic blood pressure 2.81 mmHg lower overall, 7.68 mmHg lower in treated hypertensives.
Meta-analysis Effects of magnesium supplementation on blood pressure: meta-analysis of 34 RCTs (2016) Foundational blood-pressure meta-analysis. Systolic pressure 2.00 mmHg lower, with the effect amplified in hypertensives.
Meta-analysis The effects of magnesium supplementation on glycemic control in T2DM: meta-analysis (2022) HbA1c 0.73% lower at 500 mg a day in type 2 diabetes patients.
Meta-analysis Oral magnesium supplementation for insomnia in older adults: meta-analysis (2021) Sleep onset latency 17.36 minutes shorter in elderly adults, Cohen's d around 1.1.
RCT Role of magnesium supplementation in the treatment of depression: a randomized clinical trial (2017) Open-label randomized trial in 126 adults. PHQ-9 down 6.0 and GAD-7 down 4.5 in two weeks, NNT around 3.
Meta-analysis Effects of intravenous and oral magnesium on reducing migraine: meta-analysis (2016) Migraine frequency odds ratio 0.20 across intravenous and oral magnesium trials.
Review Magnesium in man: implications for health and disease (2015) Foundational physiology review documenting magnesium's role in 600 or more enzymatic reactions, including the ATP-Mg complex.
Meta-analysis Dietary magnesium intake and the risk of cardiovascular disease, type 2 diabetes, and all-cause mortality: dose-response meta-analysis (2016) Cohort meta-analysis. 36% lower type 2 diabetes risk at the highest dietary intake quintile.
Systematic review Bioavailability of magnesium food supplements: systematic review (2021) Form-by-form bioavailability comparison. Organic chelates, including glycinate, outperform oxide.
Systematic review The effect of glycine administration on the characteristics of physiological systems in human adults: A systematic review (2024) 47 articles describing 50 studies, including 42 RCTs. The nervous-system signal was the most positive, and larger well-controlled RCTs are still needed.
RCT New therapeutic strategy for amino acid medicine: glycine improves the quality of sleep (2012) Supports the glycine sleep-quality claim at the 3 g pre-bed dose.
Mechanistic The Sleep-Promoting and Hypothermic Effects of Glycine are Mediated by NMDA Receptors in the Suprachiasmatic Nucleus (2015) Mechanistic sleep and thermoregulation work. Includes animal data rather than a large human efficacy trial.
Review Glycine as a conditionally essential amino acid and its relationship to L-serine (2025) Modern review of glycine deficiency states, glutathione, collagen and one-carbon units. Calls for controlled high-dose trials.
Review Roles of dietary glycine, proline, and hydroxyproline in collagen synthesis and animal growth (2018) Collagen biology review supporting glycine's substrate role. Much of the evidence comes from animal and growth contexts.
Mechanistic High glycine concentration increases collagen synthesis by articular chondrocytes in vitro (2018) In vitro chondrocyte study. Mechanistic support for the joint and connective-tissue rationale.
Trial Metabolic impact of dietary glycine supplementation in individuals with severe obesity (2025) Single-arm study in 19 people with severe obesity. Improved selected metabolic markers but no change in body weight, insulin resistance, red-cell glutathione or oxidative-stress markers.
RCT Effects of glycine and N-acetylcysteine on glutathione levels and mitochondrial energy metabolism in healthy aging (2021) RCT abstract in 114 healthy older volunteers. The primary circulating glutathione endpoint was not increased against placebo, with responder subgroup signals only.
RCT Supplementing Glycine and N-Acetylcysteine in Older Adults Improves Glutathione Deficiency, Oxidative Stress, Mitochondrial Dysfunction, Inflammation, Physical Function, and Aging Hallmarks: A Randomized Clinical Trial (2023) 16-week GlyNAC trial in older adults. Tests glycine plus NAC together, so it is not evidence for glycine alone.
RCT Oral supplementation with glycine reduces oxidative stress in patients with metabolic syndrome, improving their systolic blood pressure (2013) Randomized controlled trial using 5 g a day of glycine in metabolic syndrome.
RCT Placebo-controlled trial of glycine added to clozapine in schizophrenia (2000) Glycine added to clozapine produced no statistically significant symptom or cognitive improvement.

Glossary

Quick reference for the medical and technical terms used in this comparison.

NMDA N-methyl-D-aspartate receptor: An excitatory brain receptor both compounds touch from opposite sides. Glycine is a co-agonist at its glycine site. Magnesium physically blocks its pore in a voltage-dependent way.
GlyR Glycine receptor: An inhibitory chloride channel that glycine activates directly. This is the calming, sleep-onset side of glycine's action, separate from its substrate roles.
Elemental magnesium Elemental magnesium: The weight of actual magnesium in a capsule, as opposed to the weight of the whole compound. 1,000 mg of magnesium threonate is 144 mg elemental. Always compare this number.
Chelate Chelate: A mineral bound to an organic carrier molecule. Magnesium glycinate is magnesium chelated to glycine, which is why taking it means taking both compounds at once.
GlyNAC Glycine plus N-acetylcysteine: A combined protocol, not glycine alone. Kumar 2023 tested it for 16 weeks in older adults, so its results cannot be attributed to glycine by itself.
HbA1c Glycated hemoglobin: A 2 to 3 month average of blood glucose. Asbaghi 2022 found it 0.73% lower on 500 mg a day of magnesium in type 2 diabetes.
PHQ-9 Patient Health Questionnaire-9: A nine-item depression screening score. Tarleton 2017 reported it falling 6.0 points in two weeks on magnesium in an open-label randomized trial.
SBP Systolic blood pressure: The top number in a blood-pressure reading. Argeros 2025 found it 2.81 mmHg lower overall on magnesium and 7.68 mmHg lower in people already on treatment.
eGFR Estimated glomerular filtration rate: A measure of kidney filtering capacity. Below 30 is the threshold where magnesium supplementation needs nephrology oversight, because the kidney clears it.
NHANES National Health and Nutrition Examination Survey: The US population nutrition survey behind the finding that roughly 50% of American adults fall below the magnesium RDA.

Nick Urban Health Optimization Researcher & CHEK Holistic Lifestyle Coach Level 2

I've spent over a decade testing supplements on myself and screening them for clients and podcast guests

Reviewed Sep 8, 2026 · next review Dec 7, 2026

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