Magnesium Citrate

Magnesium citrate is elemental magnesium bound to citric acid. It’s one of the most common and best-value supplemental forms: reasonably high in elemental magnesium (~16%), well absorbed, and effective for general repletion — with a mild-to-moderate laxative effect that’s welcome for constipation but can mean loose stools at higher doses. For the mineral’s full evidence base, see Magnesium.

Absorption & Tolerability

Citrate is better absorbed than magnesium oxide — the classic comparison showing organic and soluble salts outperform oxide on absorption ^{1Reference 1Firoz M · 2001Clinical trialBioavailability of US commercial magnesium preparations — comparative human studyView study →} — and a small single-dose crossover study found higher urinary and serum magnesium after citrate than oxide, though it was industry-sponsored and short ^{2Reference 2Kappeler D et al. · 2017RCTHigher bioavailability of magnesium citrate versus oxide by urinary excretion and serum levels after single-dose administration — randomised crossover study (industry-sponsored, n=20)View study →}. Gut tolerance is the main constraint: as with all magnesium, the osmotic laxative effect scales with dose, so citrate is best split and taken with food if loose stools are a problem.

What the Evidence Says

Citrate is a frequent choice in magnesium trials, so much of the general magnesium evidence — modest benefits for blood pressure, blood sugar and migraine, clearest in deficient people — is representative of what citrate delivers (see Magnesium). There is little that is uniquely “citrate” about those outcomes beyond its reliable absorption.

Gap: its advantages (absorption, cost) are established, but there’s no strong evidence citrate produces better clinical outcomes than other well-absorbed forms — only better than oxide on absorption.

Dosage

Typical supplemental doses are 120–300 mg of elemental magnesium, divided; higher single doses act as a saline laxative. Commonly used ranges, not a personal recommendation — see Magnesium for the RDA and upper limit.

Safety

Well tolerated at moderate doses; diarrhea is the dose-limiting effect. General magnesium cautions apply — avoid unsupervised use in kidney impairment, and separate from bisphosphonates/certain antibiotics by ≥2 hours (see Magnesium).

References

1. Firoz M, Graber M. (2001). Bioavailability of US commercial magnesium preparations — comparative human study. Magnesium Research, 14(4), 257–262. https://pubmed.ncbi.nlm.nih.gov/11794633/
2. Kappeler D, Heimbeck I, Herpich C, et al. (2017). Higher bioavailability of magnesium citrate versus oxide by urinary excretion and serum levels after single-dose administration — randomised crossover study (industry-sponsored, n=20). BMC Nutrition, 3, 7. https://doi.org/10.1186/s40795-016-0121-3