§.01The short answer.
Both supplements are magnesium ion bonded to a carrier molecule. The carrier changes how much magnesium your gut absorbs, what stays absorbed, and what side effects you can expect.
Glycinate calms. Citrate moves. If your goal is sleep, anxiety, cramps, or general repletion, you want glycinate. If your goal is unambiguously to support a sluggish bowel, you want citrate. There is no third interpretation that this article is going to invent.
Most of the secondary questions about magnesium are really questions about glycinate. The PPI patient, the cortisol reader, the MTHFR community: glycinate fits the use case 9 out of 10 times. Dr. Marthe Janssen, PharmD
§.02The actual chemistry difference.
Magnesium glycinate is magnesium bonded to two glycine molecules. By weight, the compound is about 14% elemental magnesium. A 400 mg glycinate capsule delivers ~56 mg of elemental magnesium. Glycine itself has mild calming activity at the GABA receptor (Bannai & Kawai, 2012). You absorb both halves, and both halves do something useful. That is the entire reason glycinate gets the "sleep and anxiety" reputation.
Magnesium citrate is magnesium bonded to citric acid. By weight, it is about 16% elemental magnesium. A 400 mg citrate dose delivers ~64 mg elemental. The citrate ion is osmotically active in the gut, which is the technical way of saying it pulls water into the colon. That is also why high doses of citrate are sold as a laxative under brand names like Citroma (NIH ODS Magnesium Fact Sheet).
Head-to-head bioavailability is similar: somewhere in the 20% to 35% absorbed range, depending on dose and baseline status (Walker et al., 2003). The difference that matters is not absorption percentage. It is what each one does on the way through.
If you took "a magnesium supplement" and felt nothing except an emergency bathroom run, you took citrate at a laxative dose. That was not a defect. The product worked as designed. You just bought the wrong tool.
This is the most common version of the "magnesium did not work for me" story. Glycinate is the answer 90% of the time.
§.03Use glycinate when you need:
- Sleep onset and sleep quality. Glycine improves subjective sleep quality at 3 g doses (Yamadera et al., 2007). At supplement doses you get a fraction of that, but combined with magnesium's effect on NMDA receptors, the effect compounds.
- Anxiety and stress that shows up as physical tension. Magnesium status is inversely correlated with cortisol response to stressors (Pickering et al., 2020). Glycinate delivers magnesium without the gut clearing effect, so you can take a real dose without scheduling around a bathroom.
- Chronic muscle tension, restless legs, nighttime cramps. Same logic. You need a real dose, not a tiny one.
- Long-term magnesium repletion if blood work or symptoms suggest you are low.
§.04Use citrate when you need:
- Mild to moderate constipation. Standard pharmaceutical use at 200 to 300 mg of elemental magnesium per day (ACG Guideline, 2021).
- Pre-procedure bowel clearing under a clinician's direction. The 10-oz bottle at the pharmacy is for this purpose. Do not self-dose at that level.
- Cost-conscious repletion if your gut tolerates it. Citrate is cheaper per elemental mg than glycinate. Some people tolerate 200 mg of elemental citrate fine. Most do not.
§.05The PPI, MTHFR, and cortisol questions.
These three show up in every magnesium search query, and most articles dodge them. Short, specific answers.
Should you take magnesium on a PPI?
Yes, and you should ask your prescriber. Long-term proton pump inhibitor use (omeprazole, pantoprazole, esomeprazole) is associated with magnesium depletion, sometimes to the point of clinical hypomagnesemia. The FDA issued a Drug Safety Communication on this in 2011. Glycinate is the form most often used here because PPI users already have a sensitive gut and do not need the osmotic load from citrate.
Which magnesium is best to lower cortisol?
Glycinate, for two reasons. First, magnesium status is associated with a blunted cortisol response to stress regardless of form. Second, glycine has its own modest cortisol-modulating activity. You will not see a dramatic drop in morning cortisol from any supplement. You will see better stress recovery curves over weeks. The form does not move the needle as much as the dose and consistency do.
Can you take magnesium with MTHFR?
Yes. Magnesium and the MTHFR methylation cycle do not directly conflict. Magnesium is a cofactor for hundreds of enzymes, including some methylation-adjacent ones. People with MTHFR variants often run low in magnesium for the same reason they run low on everything: their food intake does not cover what their methylation cycle uses. Glycinate is the standard pick because it spares gut function.
Can you take glycinate and citrate together?
Yes, but it is rarely useful. If you want both sleep support and a gentle laxative effect, take glycinate in the evening and citrate in the morning. Combined doses under 500 mg elemental magnesium per day are safe for healthy adults. Above that, diarrhea is likely regardless of form.
PuraVigor's magnesium glycinate is 400 mg bisglycinate per cap, delivering ~56 mg elemental. Two capsules at dinner gets most adults into the clinically meaningful range without crossing into gut effects.
§.06Side effects, edge cases, who should skip.
- SSRIs. Talk to your prescriber. The data on magnesium with SSRIs is fine; the data with bipolar medications is more nuanced.
- Stage 4 or 5 chronic kidney disease. Magnesium is renally excreted. Do not supplement without nephrology input.
- Pregnancy. Pick glycinate over citrate (citrate's bowel effect plus pregnancy is rough). Confirm with your OB.
- Antibiotics and thyroid medication. Magnesium binds tetracyclines, fluoroquinolones, and levothyroxine in the gut. Separate doses by at least 2 hours.
- Loose stools at any dose. Dose-dependent and form-dependent. Drop the dose or switch from citrate to glycinate.
§.07Frequently asked, plainly answered.
What about magnesium oxide, the cheap option?
Oxide is ~60% elemental magnesium by weight, which sounds great until you learn that only about 4% of it gets absorbed. The math works out to less bioavailable elemental magnesium per dose than glycinate or citrate. Fine as a generic mineral, poor as a therapeutic supplement.
What about magnesium L-threonate?
Marketed for cognition because it crosses the blood-brain barrier more readily in animal studies. Human data is thinner. For sleep, anxiety, and general repletion, glycinate is more evidence-backed and cheaper per elemental mg. Threonate is a reasonable add-on if cognition is your specific goal, not a replacement.
Glycinate or bisglycinate, are they different?
Same molecule, different naming convention. "Bisglycinate" emphasizes the 2:1 glycine-to-magnesium ratio. Brands selling "magnesium glycinate" and "magnesium bisglycinate" are selling the same thing.
Can you take it with food?
Glycinate, yes, any time. Citrate, take on an empty stomach if you want the laxative effect, with food if you want to dampen it.
How long until it works?
Sleep effects from glycinate: 3 to 14 nights. Bowel effects from citrate: same day. Tissue repletion from chronic deficiency: 4 to 8 weeks.
Should you check magnesium levels with a blood test?
Serum magnesium is a poor marker; the body keeps blood levels stable by pulling from bone and muscle stores. RBC magnesium is more useful but rarely ordered. Most people supplement based on symptoms and food intake, not labs.
§.08The bottom line.
Glycinate is the answer for almost everything that brought you to this article. Citrate is the answer if you are looking at a bowel-clearing problem. If the keyword that landed you here was "sleep", "anxiety", "PPI", "MTHFR", or "cortisol", glycinate. If it was "constipation" or "bowel prep", citrate.
PuraVigor makes a glycinate. We do not make a citrate. If citrate is what you genuinely need, buy it as a generic at the pharmacy. We would rather lose the sale than sell you the wrong tool.
Magnesium Bisglycinate, 60 ct — at the apothecary.
Reviewed by Dr. Marthe Janssen, PharmD. Last updated May 17, 2026.
Disclaimer: this article is educational and does not substitute for advice from your prescriber. Statements have not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any disease.