There are at least 11 different forms of supplemental magnesium. Walk into any health store and you'll find glycinate, citrate, oxide, threonate, taurate, malate, orotate, chloride—the list keeps going. Each has a different absorption rate, different side effects, and different use cases.
Most people searching "magnesium glycinate vs citrate" want a simple answer. Here it is: glycinate is better for sleep, anxiety, and general supplementation. Citrate is better for constipation and is a solid all-rounder. Oxide is cheap but mostly useless for anything except loosening your bowels.
But there's more to it than that. Let's break down every major form.
Magnesium is never supplemented alone. It's always bonded to another molecule—an amino acid, an organic acid, or an inorganic compound. This "carrier" determines three things:
A 500mg tablet of magnesium oxide contains about 300mg of elemental magnesium but your body absorbs roughly 4% of it. A 500mg tablet of magnesium glycinate contains about 70mg of elemental magnesium but your body absorbs closer to 80%. Do the math: you're actually getting more usable magnesium from the glycinate despite the lower label number.
This is the single most confusing thing about magnesium supplements. You have to look at elemental magnesium content, not total milligrams of the compound.
Magnesium bonded to two glycine molecules. This is the form most recommended by integrative and functional medicine practitioners, and for good reason.
High bioavailability. A 2014 study in Magnesium Research compared several organic magnesium salts and found glycinate among the best absorbed. Because it uses the amino acid transport pathway rather than relying on passive diffusion, absorption stays relatively stable even at higher doses.
Excellent. Glycinate is the form least likely to cause diarrhea or cramping. This makes it ideal for people who need higher magnesium doses or who have sensitive stomachs.
Glycine itself is an inhibitory neurotransmitter. At 3g doses, it's been shown to improve sleep quality in small studies. You won't get 3g from a standard magnesium glycinate dose, but you're still getting a meaningful amount—roughly 1-1.5g of glycine from a typical 400mg elemental magnesium dose. This probably contributes to the calming effect people report.
Typical dose: 200-400mg elemental magnesium. Labels often list the total compound weight, so read carefully. You want the "elemental magnesium" number.
Magnesium bonded to citric acid. This is the pharmacy workhorse—widely available, well-absorbed, and reasonably priced.
Good. A 2003 study in Magnesium Research found magnesium citrate had significantly higher bioavailability than magnesium oxide. It's not quite as well-absorbed as glycinate in most comparisons, but the difference is modest.
This is the important distinction. Citrate has a mild osmotic laxative effect. It draws water into the intestines. For people with constipation, this is a feature. For everyone else, it can be an inconvenience—especially at doses above 300mg.
If you've ever done colonoscopy prep, you've had a large dose of magnesium citrate. At supplemental doses it's much gentler, but the mechanism is the same.
Typical dose: 200-400mg elemental magnesium. Start lower if you're concerned about GI effects.
| Feature | Glycinate | Citrate |
|---|---|---|
| Bioavailability | High (~80%) | Good (~25-30%) |
| GI tolerance | Excellent | Moderate (laxative at higher doses) |
| Sleep support | Strong (glycine component) | Moderate |
| Constipation relief | Minimal | Good |
| Cost | $$ | $ |
| Availability | Health stores, online | Everywhere |
| Taste (powder form) | Mildly sweet | Tart/sour |
The form you'll find in most cheap multivitamins and drugstore magnesium tablets. Contains the highest percentage of elemental magnesium per pill (about 60%), but bioavailability is abysmal—roughly 4% in a 2001 study published in the Journal of the American College of Nutrition.
The math doesn't work in its favor. A 400mg magnesium oxide tablet delivers ~240mg elemental magnesium. At 4% absorption, you're getting roughly 10mg. A 400mg glycinate with 70mg elemental magnesium at 80% absorption gives you ~56mg. Oxide loses, badly.
Its primary legitimate use is as an osmotic laxative.
This one has gotten a lot of attention from the biohacking crowd, largely because of Andrew Huberman. The pitch: threonate crosses the blood-brain barrier more effectively, so it should be better for cognitive function and brain health.
The evidence is early. A 2010 study in Neuron showed that magnesium threonate increased brain magnesium levels and improved learning and memory in rats. A 2016 human trial in the Journal of Alzheimer's Disease found improvements in cognitive abilities in older adults with cognitive concerns.
Promising, but limited. And it's expensive—often 3-5x the cost of glycinate per serving. The elemental magnesium content is also quite low (~8%), so you need a lot of capsules.
Bonded to taurine, which has its own cardiovascular benefits. Some preliminary research suggests taurate may support blood pressure and heart health. A 2018 study in Biological Trace Element Research found that magnesium taurate was more effective at preventing elevated blood pressure than magnesium oxide in animal models.
Good option if cardiovascular support is your primary goal. Absorption is similar to glycinate.
Bonded to malic acid, which plays a role in the Krebs cycle (energy production). Sometimes recommended for fatigue and fibromyalgia based on a small 1995 study, but the evidence is thin. Reasonably well-absorbed. Some people prefer it as a daytime magnesium because it doesn't have the sedating effect of glycine.
| Form | Absorption | Best For | GI Tolerance | Cost |
|---|---|---|---|---|
| Glycinate | High | Sleep, anxiety, general | Excellent | $$ |
| Citrate | Good | General, constipation | Moderate | $ |
| Threonate | Good (brain) | Cognition, memory | Good | $$$ |
| Taurate | Good | Heart health, BP | Good | $$ |
| Malate | Good | Energy, fatigue | Good | $$ |
| Oxide | Very low (~4%) | Laxative only | Poor | $ |
| Chloride | Moderate | Topical, digestion | Moderate | $ |
The RDA varies by age and sex:
These numbers include dietary magnesium. Good food sources: pumpkin seeds (156mg per ounce), spinach (78mg per half cup cooked), dark chocolate (65mg per ounce), almonds (80mg per ounce).
The NIH's tolerable upper intake from supplements is 350mg/day of elemental magnesium. Going above this isn't necessarily dangerous for most people, but it increases the risk of GI side effects, particularly with non-glycinate forms.
USDA data consistently shows that about 50% of Americans don't meet the RDA through diet alone. If your diet is heavy on processed foods and light on nuts, seeds, leafy greens, and whole grains, you're probably in that group.
Look, this doesn't need to be complicated:
When reading labels, always check for "elemental magnesium" content. If the label just says "magnesium (as magnesium glycinate) 500mg," that 500mg is the compound weight. The actual elemental magnesium is roughly 14% of that for glycinate, so about 70mg. Good brands list this clearly. Unclear labeling is a red flag.
Scan or search 200,000+ supplements for safety, efficacy, and transparency scores.
Download Suppi Free