Magnesium (Glycinate & Citrate)
Magnesium is a mineral your body uses for hundreds of jobs, including muscle and nerve function and blood sugar and blood pressure control. In a small review of older adults, it helped people fall asleep a little faster, but the evidence was rated low quality. It may also help prevent migraines.
Magnesium is a mineral that more than 300 enzyme systems in the body depend on, including those for protein synthesis, muscle and nerve function, blood sugar control and blood pressure. The body also needs it to produce energy. Glycinate and citrate are two supplement forms. Small studies have found that citrate is absorbed more completely than magnesium oxide or sulfate, and it's also sold as a saline laxative for occasional constipation. NIH and MSK describe magnesium in general; they don't cover the glycinate form specifically.
Research & evidence
Strong support Some support Weak or no supportColours show how well the sources back each point. The reason is next to each one.
In older adults, magnesium supplementation modestly reduced sleep onset latency in a small systematic review and meta-analysis, though evidence quality was rated low, and effects on subjective sleep quality were inconclusive.
Limited evidenceSome support. Reviewers rated the certainty low
Study details
A single systematic review (3 small RCTs, n=151, older adults only) found a statistically significant reduction in sleep onset latency, but GRADE-rated the evidence low-to-very-low quality; subjective sleep quality results were mixed/indeterminate across the two questionnaire-based trials.
Source: Mah J, Pitre T. Oral magnesium supplementation for insomnia in older adults: a Systematic Review & Meta-Analysis. BMC Complement Med Ther. 2021;21:125. View source
Magnesium supplementation may reduce the frequency of migraine attacks.
Moderate evidenceSome support. Based on one or a few small trials
Study details
3 of 4 small, short-term placebo-controlled trials showed reduced migraine frequency at doses up to 600 mg/day; the American Academy of Neurology and American Headache Society evidence-based guideline concludes magnesium therapy is "probably effective" for migraine prevention.
Source: NIH Office of Dietary Supplements, Magnesium — Health Professional Fact Sheet, "Migraine headaches" section View source
Magnesium citrate is an FDA-labeled saline laxative used for relief of occasional constipation, typically producing a bowel movement within 1/2 to 6 hours. It has also been studied off-label for pre-colonoscopy bowel preparation — though only as part of a combination regimen with the stimulant laxative bisacodyl (MCCB), tested in a single small proof-of-concept trial, not as magnesium citrate alone.
Strong evidenceStrong support. Stated plainly by NIH or an FDA label
Study details
An FDA over-the-counter drug label lists magnesium citrate as a saline laxative for occasional constipation. For pre-colonoscopy bowel prep, the only support is a single small (n=51), single-center RCT testing magnesium citrate combined with bisacodyl (MCCB), which the study authors themselves describe as "proof of concept only," not evidence of magnesium citrate alone being effective for bowel prep.
Source: FDA OTC Drug Label (DailyMed), Magnesium Citrate Oral Solution, Purpose: Saline Laxative; and Eidensohn Y, Mond Y, Labowitz I, et al. "Magnesium Citrate Capsules in Colonoscopy Preparation: A Randomized Controlled Trial." Cureus. 2021 Dec 18. DOI: 10.7759/cureus.20506. View source
Dosage
| Form | Amount |
|---|---|
| Any form | Recommended daily amounts for adults: men, 400 mg (ages 19–30) and 420 mg (31 and older); women, 310 mg (19–30) and 320 mg (31 and older). The upper limit for magnesium from supplements and medications is 350 mg a day for adults; it doesn't include magnesium from food. The forms most often reported to cause diarrhea are magnesium carbonate, chloride, gluconate and oxide. |
Side effects
The most common problem is diarrhea from high doses, sometimes with nausea and cramps. Very large doses of magnesium-containing laxatives or antacids have been linked to magnesium toxicity, which can be dangerous, especially if your kidneys don't work well.
Well documented Reported (case reports, anecdotal or one study) None reportedThe circle shows how well documented an effect is, not how serious it is. A rarely reported effect can still be serious, so always read ‘When to stop’.
| Effect | Frequency | When to stop |
|---|---|---|
| Diarrhea, sometimes with nausea and stomach crampsWell documentedListed plainly by NIH, MSK or LiverTox | Often, with high doses | Lower the dose or stop, and talk to a doctor if it doesn't settle. |
| Mild stomach or bone painWell documentedListed plainly by NIH, MSK or LiverTox | With high doses | Stop and talk to a doctor if it persists. |
| Magnesium toxicity (low blood pressure, vomiting, trouble breathing, irregular heartbeat)Well documentedListed plainly by NIH, MSK or LiverTox | Relatively rare; linked to very large doses of laxatives or antacids, and more likely with kidney problems | Get medical help right away if these happen. |
Safety & interactions
Safety
High doses of magnesium from supplements or medications often cause diarrhea, which can come with nausea and stomach cramps. The upper limit for adults is 350 mg a day of supplemental magnesium; it doesn't include magnesium from food. Very large doses of magnesium-containing laxatives and antacids (typically more than 5,000 mg a day) have been linked to magnesium toxicity, which can cause low blood pressure, vomiting, trouble breathing, irregular heartbeat and cardiac arrest. The risk is higher if your kidneys don't work well.
Contraindications
MSK says not to take magnesium supplements if you have kidney problems (such as renal insufficiency or end-stage renal disease), a bowel obstruction or other bowel disorder, or heart block (a problem with the heart's electrical signals), or if you take medicines for heart disease (your doctor should monitor your magnesium and other electrolyte levels). MSK's list also includes taking antibiotics, blood pressure drugs including calcium channel blockers, or sulfonylurea diabetes drugs; see Drug interactions. People with other heart, kidney or digestive disorders should take magnesium supplements only under a doctor's supervision.
Drug interactions
Magnesium forms complexes with tetracycline and quinolone antibiotics, reducing their absorption. Take the antibiotic at least 2 hours before, or 4 to 6 hours after, a magnesium-containing supplement. (The nitrofurantoin interaction comes from a single source.)
Magnesium-rich supplements can decrease the absorption of oral bisphosphonates. Separate the two by at least 2 hours in either direction.
IV magnesium sulfate given during surgery is well documented to potentiate neuromuscular blocking agents — shortening onset time and prolonging their effect (anesthesiologists sometimes use this intentionally as an adjuvant). Whether taking an oral magnesium supplement has a similar effect hasn't been directly studied — the evidence base, including Memorial Sloan Kettering's own cited sources, covers only IV magnesium given in clinical/surgical settings. As a precaution, tell your surgeon or anesthesiologist if you take magnesium supplements, the same way you'd disclose any supplement before surgery. This does not describe oral muscle relaxants such as cyclobenzaprine or baclofen.
MSK says magnesium-containing products may have an additive effect on blood pressure when taken with calcium channel blockers. MSK's only reference for this is a review of high blood pressure in pregnancy.
These diuretics increase magnesium loss in urine and can lead to magnesium depletion with long-term use.
Potassium-sparing diuretics reduce magnesium excretion, which can raise magnesium levels — the opposite effect from loop and thiazide diuretics.
Long-term prescription PPI use (typically more than a year) can cause low blood magnesium (hypomagnesemia). The FDA advises checking serum magnesium before starting long-term PPI treatment and periodically during use.
Magnesium supplements or antacids can increase how fast and how much sulfonylurea drugs are absorbed (MSK, citing a 1994 review of antacid drug interactions). MSK's patient guidance says not to take magnesium with them, because it may cause low blood sugar.
Established: stated plainly by an authoritative source. Documented: supported by case reports or trial data. Theoretical: based on mechanism, animal data, or a cautious listing. Always check with your pharmacist or prescriber.
Combining with other herbs
Avoid combining with
Which form to buy
Magnesium citrate, chloride, aspartate or lactate
Good choiceAbsorbed better than other forms (per NIH)
Small studies found these forms are absorbed more completely than oxide or sulfate. Chloride is also one of the forms most often reported to cause diarrhea.
Magnesium oxide
Weaker choiceAbsorbed less well than other forms
Absorbed less completely than citrate, chloride, aspartate or lactate, and one of the forms most often reported to cause diarrhea.
Magnesium glycinate
Not comparedOur sources don't compare this form
Our sources don't compare glycinate with other forms.