Magnesium
Also known as: Mg, Magnesium glycinate, Magnesium citrate
An essential mineral involved in more than 300 enzyme reactions, widely supplemented for sleep, muscle, and nerve function.
Magnesium is an essential mineral, and supplementation clearly helps when intake or status is low. Specific magnesium salts also have established laxative uses, while evidence for sleep is low-certainty and evidence for routine cramp prevention in otherwise healthy adults is insufficient.1
- Cofactor in more than 300 enzyme systems in the body1
- Found in leafy greens, nuts, seeds, legumes, and whole grains1
- Recommended intake: 400–420 mg daily for men, 310–320 mg for women1
- Supplement forms vary in absorption and laxative effect1
What is Magnesium?
Magnesium is the fourth most abundant mineral in the human body. About half is stored in bone, and the rest is in muscles, soft tissues, and a small but tightly regulated amount in blood. It is needed for energy production (ATP), DNA and RNA synthesis, muscle contraction, and nerve signaling. Because refined Western diets tend to be low in magnesium-rich foods, surveys consistently estimate that many Americans consume less than the recommended amount, making magnesium supplements a staple of the supplement market.1
Where it comes from
Natural sources
- Leafy green vegetables such as spinach
- Nuts and seeds, especially pumpkin seeds and almonds
- Legumes, beans, and whole grains
- Dark chocolate and some mineral waters
How it's made
Supplemental magnesium is mined or extracted and combined with other molecules (glycine, citric acid, etc.) to form salts with different absorption profiles.
What it does in products
Benefits
Correcting deficiency and inadequate intake
strong evidenceLow magnesium intake is associated with a higher risk of hypertension, type 2 diabetes, and osteoporosis. Supplementation reliably raises blood magnesium in people with low intake.1
Magnesium is an essential nutrient; supplementation corrects low intake or deficiency, while disease-prevention claims in replete people are a separate question.
Constipation relief
strong evidenceMagnesium oxide and citrate draw water into the intestines, acting as osmotic laxatives. Magnesium citrate and hydroxide solutions are used medically for occasional constipation.2, 1
The joint AGA-ACG guideline conditionally recommends magnesium oxide for chronic idiopathic constipation, with low-certainty evidence and renal-safety cautions.
Sleep support
limited evidenceMagnesium is involved in nervous-system calming, and some small trials suggest supplementation modestly improves sleep quality, particularly in older adults and people with low intake.3
The review found only three small trials in older adults, all with moderate-to-high risk of bias and low or very-low certainty.
Muscle cramps and recovery
insufficient evidenceMagnesium is often marketed for cramps, but a Cochrane review found little evidence of a clinically meaningful benefit for idiopathic cramps in older adults; deficiency is a separate indication.4, 1
Results differ by population, and evidence in pregnancy-associated or exercise-associated cramps remains too limited for a general recommendation.
Evidence scope and limitations
The evidence review distinguishes correction of inadequate magnesium status, medically used magnesium salts, and supplementation in otherwise replete adults.
- Different magnesium salts have different elemental amounts, absorption, and laxative effects.
- Sleep and cramp studies are small and should not be generalized to all adults or all magnesium products.
Evidence last checked: 2026-09-26
Side effects & safety
Safety considerations
- Magnesium is safe in pregnancy at standard supplement doses and is used to treat preeclampsia in medical settings. Stay within the 350 mg supplement upper limit unless advised otherwise.
- Magnesium can reduce absorption of certain antibiotics (tetracyclines, quinolones); separate doses by at least 2 hours.
- It can also reduce absorption of bisphosphonates used for osteoporosis; take these well apart.
- Not for: Advanced kidney disease (magnesium can accumulate when kidneys cannot excrete it)
Amounts studied & product use
These figures describe research or common product use, not a personal dose or treatment recommendation.
In supplement studies and products
The U.S. RDA is 400–420 mg per day for adult men and 310–320 mg for adult women from all sources; the 350 mg upper limit applies to supplemental magnesium, not food. Sleep and bowel studies use different salts and doses, so they do not establish one general-purpose magnesium dose.
Regulatory status
- Dietary supplement regulated by the FDA under DSHEA. Manufacturers are responsible for safety and accurate labeling; no pre-market approval is required.
- GRAS (generally recognized as safe) for food use.
Choosing a magnesium form
Magnesium is always sold as a salt — the mineral bound to another molecule. The binding molecule affects absorption, tolerated dose, and side effects. Glycinate is well absorbed and gentle on the stomach, making it a common default. Citrate is well absorbed and has a mild laxative effect. Oxide is cheap and contains the most elemental magnesium per gram, but is poorly absorbed and used mainly as a laxative. L-threonate is marketed for brain health and crosses the blood-brain barrier more readily in animal studies, though it is more expensive.
| Form | Elemental Mg | Absorption | Typical use |
|---|---|---|---|
| Glycinate | ~14% | High | General use, sleep, muscle |
| Citrate | ~16% | High | Regularity, general use |
| Oxide | ~60% | Low | Laxative, heartburn relief |
| L-threonate | ~8% | High | Cognition-focused products |
Frequently asked questions
Which magnesium is best for sleep?
Magnesium glycinate is the most common choice for sleep support because it is well absorbed and unlikely to cause diarrhea. Evidence for a sleep benefit is modest but the risk is low; many people also pair it with glycine, which may independently support relaxation.1
Can I take magnesium every day?
Yes. For most adults, 200–350 mg daily from supplements is safe long-term. Keep total supplement intake at or below 350 mg unless a healthcare provider recommends more, and reduce the dose if you develop loose stools.1
Does magnesium interfere with medications?
It can. Magnesium can reduce the absorption of certain antibiotics and osteoporosis drugs, so take those medications at least 2 hours apart from magnesium. If you take diuretics, heart medication, or have kidney disease, check with your doctor first.1
The bottom line
Magnesium is most defensible for correcting inadequate status or for a salt-specific medical use. Sleep, cramp, and recovery claims need more caution than the category's popularity implies.
References
- Magnesium: Health Professional Fact Sheet. NIH Office of Dietary Supplements (2025) · government guidance
- AGA-ACG Clinical Practice Guideline: Pharmacological Management of Chronic Idiopathic Constipation. Gastroenterology (2023) · clinical guideline · PMID 37211380
- Oral magnesium supplementation for insomnia in older adults: a systematic review and meta-analysis. BMC Complementary Medicine and Therapies (2021) · meta analysis · PMID 33865376
- Magnesium for skeletal muscle cramps. Cochrane Database of Systematic Reviews (2020) · systematic review · PMID 32956536
- Dietary Supplements. U.S. Food and Drug Administration (2025) · government guidance
Revision history
- Replaced search-result citations with exact sources, mapped claims to evidence, and reassessed evidence strength.