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Magnesium Citrate

Evidence Level
Strong
2 Clinical Trials
5 Documented Benefits
4/5 Evidence Score

Magnesium citrate is a well-absorbed and popular form of magnesium in which the mineral is bound to citric acid. It is used both to raise magnesium levels, supporting muscle and nerve function, energy, sleep, and relaxation, and, at higher doses, as a gentle osmotic laxative for occasional constipation, since it draws water into the intestines. This dual nature means it can loosen stools, so those wanting magnesium without a laxative effect often choose magnesium glycinate instead. A typical dose provides around 100 to 200 mg of elemental magnesium; check the label, as the elemental content is lower than the total compound weight.

Studied Dose 200–400 mg elemental magnesium/day for general supplementation; 150–300 mL of 1.745 g/30 mL solution for bowel prep
Active Compound Magnesium citrate

Benefits

High Bioavailability

Magnesium citrate is consistently rated among the most bioavailable forms — citric acid enhances solubility at gastric pH and forms a soluble complex absorbed in the small intestine. Comparable to glycinate; substantially better than oxide.

Supported by Trial 1

Constipation Relief

Magnesium citrate's osmotic effect draws water into the bowel, softening stool and promoting bowel movement. Doses of 200–600 mg elemental magnesium typically relieve mild constipation; high-dose (300 mL of 1.745 g/30 mL solution) is used for bowel preparation before colonoscopy.

Supported by Trial 1

Magnesium Deficiency Correction

Effective for replenishing magnesium status in deficient populations. Trials show meaningful increases in serum/RBC magnesium with daily supplementation.

Supported by Trial 1, Trial 2

Migraine Prevention

Magnesium (citrate or other forms) at 400-600 mg daily is supported by AHS/AAN guidelines (Level B) for episodic migraine prevention.

Supported by Trial 2

Kidney Stone Prevention

Magnesium citrate may modestly reduce calcium oxalate kidney stone formation — citrate inhibits calcium oxalate crystallization independently. Better-evidenced for potassium citrate but magnesium citrate is sometimes used.

Supported by Trial 2, Trial 1

Mechanism of action

1

Citric Acid Solubilization

Citric acid's three carboxyl groups complex with magnesium, maintaining solubility across gastric pH changes and improving absorption via standard divalent cation pathways.

2

Osmotic Bowel Effect

Unabsorbed magnesium and citrate ions in the bowel pull water into the lumen via osmosis, increasing stool volume and softening — laxative effect at higher doses.

3

NMDA Receptor and Calcium Channel Modulation

Magnesium gates NMDA receptors and modulates voltage-gated calcium channels in vascular smooth muscle and neurons — basis for migraine prevention and vasodilatory effects.

4

ATP Cofactor

Mg-ATP is the biologically active form of ATP; magnesium is required cofactor for >300 enzymes including all ATPases.

Clinical trials

1
Magnesium Citrate Bioavailability

Crossover trial comparing magnesium citrate, glycinate, and oxide bioavailability in healthy adults. Outcomes: serum magnesium, urinary excretion, RBC magnesium. (Magnes Res)

Healthy adults.

Magnesium citrate produced significantly higher absorption vs oxide; comparable to glycinate. Higher 24-hour urinary excretion confirmed superior absorption. Established citrate as among the most bioavailable forms.

2
Magnesium for Migraine Prevention — Köseoglu 2008

Clinical trial of magnesium citrate (600 mg/day) vs placebo in 40 migraine patients for 12 weeks. (Köseoglu et al. 2008, Magnes Res)

40 migraine patients.

Magnesium citrate significantly reduced migraine frequency, severity, and duration vs placebo. Supports magnesium's place in AHS/AAN guidelines (Level B). Diarrhea was common side effect.

Side effects and drug interactions

Common Potential side effects

Diarrhea / loose stools — primary dose-limiting side effect; especially at >400 mg elemental magnesium.
GI cramping, bloating.
Flatulence.
Dehydration possible at high doses (bowel prep amounts) — drink fluids.
Hypotension at very high doses.

Important Drug interactions

Bisphosphonates — chelation; separate by 2 hours.
Tetracycline/quinolone antibiotics — chelation; separate by 2 hours.
Levothyroxine — separate by 4 hours.
Diuretics — modulate magnesium balance.
Digoxin — laxative effect of high-dose magnesium citrate may reduce digoxin absorption; monitor.
Proton pump inhibitors — long-term cause hypomagnesemia.

Featured in these supplement guides

Bone Density→Constipation→IBS→Migraine Prevention→Muscle & Leg Cramps→Restless Legs Syndrome→Vertigo & Dizziness→

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Frequently asked questions about Magnesium Citrate

What is magnesium citrate used for?

Magnesium citrate is a well-absorbed form of magnesium used both to top up magnesium levels and, at higher doses, for its gentle laxative effect to relieve occasional constipation. It is one of the more popular and economical forms.

How much magnesium citrate should I take?

For general magnesium support, doses provide around 100 to 200 mg of elemental magnesium, up to a common daily target of about 200 to 400 mg. Higher doses are used short-term for constipation. Check the label for elemental magnesium content.

Does magnesium citrate cause diarrhea?

It can. Magnesium citrate draws water into the intestines, which is why it relieves constipation but can also cause loose stools or diarrhea at higher doses. If you want magnesium without the laxative effect, magnesium glycinate is gentler.

When should I take magnesium citrate?

For general supplementation it can be taken any time, with or without food; many take it in the evening. For constipation relief, it is taken as directed with plenty of water. Start with a lower dose to gauge your tolerance.

What is Magnesium Citrate?

Magnesium citrate is a well-absorbed and popular form of magnesium in which the mineral is bound to citric acid. It is used both to raise magnesium levels, supporting muscle and nerve function, energy, sleep, and relaxation, and, at higher doses, as a gentle osmotic laxative for occasional constipation, since it draws…

What is the recommended dosage of Magnesium Citrate?

The clinically studied dose is 200–400 mg elemental magnesium/day for general supplementation; 150–300 mL of 1.745 g/30 mL solution for bowel prep Always follow the product label and check with a healthcare provider for personal advice.

Is Magnesium Citrate safe, and does it have side effects?

For most healthy adults, Magnesium Citrate is well tolerated at studied doses. Reported effects can include: Diarrhea / loose stools — primary dose-limiting side effect; especially at >400 mg elemental magnesium. GI cramping, bloating. It may also interact with some medications. Magnesium Citrate is not right for everyone, so check with a healthcare provider first if you are pregnant or breastfeeding, have a medical condition, or take prescription medication.

Does Magnesium Citrate interact with any medications?

Possible interactions include: Bisphosphonates — chelation; separate by 2 hours. Tetracycline/quinolone antibiotics — chelation; separate by 2 hours. If you take prescription medication, check with a pharmacist or doctor before using it.

How strong is the scientific evidence for Magnesium Citrate?

NutraSmarts rates the evidence for Magnesium Citrate as Strong (4 out of 5). It is backed by 2 clinical trials and 4 cited references summarized on this page. A higher rating reflects more, larger, and better-designed human studies.

References(4 citations)

Evidence ratings on NutraSmarts are based on the totality of human clinical research, with emphasis on randomized controlled trials, meta-analyses, and systematic reviews. The references below directly support claims made throughout this page.

  1. Lindberg JS, Zobitz MM, Poindexter JR, Pak CY. Magnesium bioavailability from magnesium citrate and magnesium oxide. J Am Coll Nutr. 1990;9(1):48-55. doi: 10.1080/07315724.1990.10720349.PubMedUsed to support: Controlled human comparison showing magnesium citrate is more soluble and better absorbed (higher urinary Mg) than inexpensive magnesium oxide - supports citrate's superior bioavailability versus oxide, the central rationale for choosing the citrate form.
  2. Walker AF, Marakis G, Christie S, Byng M. Mg citrate found more bioavailable than other Mg preparations in a randomised, double-blind study. Magnes Res. 2003;16(3):183-91.PubMedUsed to support: Randomised double-blind trial finding magnesium citrate raised plasma and cellular Mg more than oxide or amino-acid chelate - supports better repletion with citrate, with the honest framing that for clinical outcomes total elemental magnesium intake usually matters more than the specific salt.
  3. Eidensohn Y, Mond Y, Labowitz I, Greenberg P, Formanowski B, Eidensohn C, et al. Magnesium Citrate Capsules in Colonoscopy Preparation: A Randomized Controlled Trial. Cureus. 2021;13(12):e20506. doi: 10.7759/cureus.20506.PubMedUsed to support: RCT using magnesium citrate as an osmotic agent for colonoscopy bowel preparation - documents the laxative use, honestly illustrating that the same osmotic mechanism that empties the bowel is why higher repletion doses of magnesium citrate cause diarrhea.
  4. Berkelhammer C, Ekambaram A, Silva RG. Low-volume oral colonoscopy bowel preparation: sodium phosphate and magnesium citrate. Gastrointest Endosc. 2002;56(1):89-94. doi: 10.1067/mge.2002.125361.PubMedUsed to support: Randomized comparison employing magnesium citrate within a low-volume osmotic bowel-prep regimen - further supports the osmotic-laxative/bowel-cleansing use of magnesium citrate and the dose-dependent diarrheal effect inherent to the form.