Magnesium Citrate

non-nutrient/non-botanical
Take with food

What is it

Magnesium citrate is magnesium bound to citric acid. It is one of the most popular magnesium supplement forms, well absorbed and inexpensive, with a mild laxative effect that makes it useful for both magnesium repletion and constipation.

How it works

In the gut, magnesium citrate dissociates and the magnesium ion is absorbed across the intestinal wall. The citrate portion is metabolized as a normal cellular fuel. Absorption is good — better than magnesium oxide — though as with all forms it decreases with larger doses. Magnesium citrate's osmotic effect draws water into the intestines, producing a softening effect on stool. At standard supplement doses (200 to 400 mg of elemental magnesium) this is mild; at much higher doses (typically prescribed as 240 mL of liquid magnesium citrate) it acts as a strong laxative used for bowel preparation.

Evidence for 5 uses

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Raising magnesium status

Grade A

Strong evidence

Magnesium citrate is consistently shown to raise serum and red blood cell magnesium more effectively than magnesium oxide.

Constipation relief

Grade A

Strong evidence

An effective osmotic laxative at appropriate doses; widely used for occasional constipation and bowel preparation.

Migraine prevention

Grade B

Good evidence

Magnesium supplementation (often citrate or other well-absorbed forms) reduces migraine frequency; the American Academy of Neurology rates it 'probably effective.'

Blood pressure

Grade B

Good evidence

Magnesium supplementation including citrate produces small but consistent blood pressure reductions, especially in people with hypertension or deficiency.

Kidney stone prevention (calcium oxalate)

Grade C

Moderate evidence

Citrate raises urinary citrate, which inhibits calcium oxalate stone formation. Magnesium citrate is sometimes used for this purpose, though potassium citrate is more commonly prescribed.

Dosage

Common supplement doses provide 100 to 400 mg of elemental magnesium per serving. Note that supplement bottles often list total magnesium citrate weight, not elemental magnesium — read the supplement facts panel. The upper limit for supplemental magnesium is 350 mg per day in adults.

When and how to take it

Magnesium citrate works well taken with food, which moderates the laxative effect and improves comfort. Many people prefer evening dosing for its calming and constipation-relieving effects on the morning following. Splitting doses (e.g., 200 mg twice daily) improves absorption and reduces digestive side effects compared to a single 400 mg dose.

Safety

Generally well tolerated. The most common side effect is loose stools or diarrhea, which is dose-dependent. People with kidney disease should not take magnesium citrate without medical supervision because excretion is impaired. People taking it regularly should be aware that citrate can modestly increase urine alkalinity, which is sometimes useful for prevention of certain kidney stones.

Who should be cautious

People with chronic kidney disease should avoid magnesium citrate without medical guidance. Those with severe diarrhea, gut motility disorders, or bowel obstruction should not use it. Pregnant women can take it safely at typical doses.

Interactions

Reduces absorption of bisphosphonates, certain antibiotics (tetracyclines, quinolones), and some thyroid medications — separate by at least 2 hours. Loop and thiazide diuretics increase magnesium loss. Proton pump inhibitors used long-term may cause magnesium deficiency that supplementation helps offset.

Frequently asked questions

Is magnesium citrate good for constipation?⌄

Yes. At standard supplement doses (200 to 400 mg) it softens stool mildly. At higher doses it acts as a strong laxative and is used clinically for bowel prep.

Does magnesium citrate cause diarrhea?⌄

It can, especially at higher doses. Splitting the dose and taking with food helps. If diarrhea persists, try magnesium glycinate, which is gentler.

How is magnesium citrate different from oxide?⌄

Citrate is absorbed much better — about 25 to 30 percent versus around 4 percent for oxide. Oxide is mostly useful as a laxative.

Can I take magnesium citrate every day?⌄

Yes, at standard doses. People with kidney disease should consult their doctor.

What time of day should I take magnesium citrate?⌄

Either time works. Many people take it in the evening for sleep support and to relieve next-morning constipation.

Track Magnesium Citrate with Pilora

Set up dose reminders, check interactions, and join the community in the Pilora iPhone app.

Coming to App Store

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you're pregnant, breastfeeding, on medications, or managing a chronic condition.