Magnesium
Also known as: Mg
Medically reviewed by Nano Health Insights Editorial Team · Last reviewed 2026-06-29
Magnesium is an essential mineral that supports over 300 enzyme systems in the body.
What it is
Magnesium is an essential mineral that supports over 300 enzyme systems in the body. It is needed for muscle and nerve function, energy production, blood glucose regulation, blood pressure control, DNA and RNA synthesis, and normal heart rhythm. An adult body contains about 25 grams of magnesium, but less than 1% is in the blood, which is why a normal blood test does not always reflect total body stores.
Magnesium is naturally present in foods such as nuts, seeds, legumes, whole grains, and green leafy vegetables. It is also available in supplements and in some medicines, including antacids and laxatives. In India, common magnesium-containing foods include dals, beans, peanuts, sesame seeds, ragi, whole grains, and green leafy vegetables, but intake can still be low when diets rely heavily on refined cereals and ultra-processed foods.
How it works
Magnesium acts as a cofactor in hundreds of biochemical reactions. It helps enzymes use ATP, the cell's main energy currency, so it is central to energy metabolism. It also helps regulate the movement of calcium and potassium across cell membranes, which affects nerve signaling, muscle contraction, and heartbeat.
About 50% to 60% of the body's magnesium is stored in bone, with most of the rest inside cells and soft tissues. The kidneys play a major role in magnesium balance by adjusting how much is excreted in urine. When intake falls or losses rise, the body can conserve magnesium for a time, but prolonged deficiency can still develop.
Common reasons magnesium levels fall include poor dietary intake, chronic diarrhea, alcohol use disorder, uncontrolled diabetes, gastrointestinal disease, and certain medicines. Drugs that can lower magnesium include loop and thiazide diuretics, proton pump inhibitors, some antibiotics, and certain chemotherapy agents.
Evidence and uses
Magnesium is best established as a nutrient needed to prevent and treat deficiency. True magnesium deficiency, or hypomagnesemia, can cause weakness, muscle cramps, tremor, abnormal heart rhythms, seizures, low calcium, and low potassium. Severe deficiency needs medical evaluation and sometimes intravenous replacement.
For people without confirmed deficiency, evidence for magnesium supplements depends on the condition being considered.
| Use | What evidence suggests |
|---|---|
| Confirmed deficiency | Clear benefit; replacement is standard care |
| Constipation or antacid use | Some magnesium salts are used in medicines, but they are not appropriate for everyone |
| Migraine prevention | Some guidelines and trials support a possible benefit in selected patients, but results are mixed |
| Blood pressure | Small reductions may occur in some people, especially if intake is low |
| Type 2 diabetes and glucose control | Low magnesium status is associated with diabetes risk, but supplementation effects are modest and not universal |
| Sleep, anxiety, muscle cramps | Evidence in humans is limited or mixed |
Observational studies often link higher magnesium intake with better cardiometabolic health, including lower risk of hypertension and type 2 diabetes. But observational links do not prove that supplements will prevent disease. In trials, benefits are usually modest and more likely when a person has low intake or low magnesium status to begin with.
Food sources are generally preferred over supplements because they provide fiber and other nutrients along with magnesium. Examples include pumpkin seeds, almonds, cashews, peanuts, soy foods, beans, oats, brown rice, spinach, and other leafy greens. In Indian diets, pulses, chana, rajma, groundnuts, til, and millets can contribute meaningful amounts.
Different supplement forms contain different amounts of elemental magnesium and are absorbed differently. Common forms include magnesium citrate, glycinate, oxide, chloride, and lactate. Magnesium oxide contains a high proportion of elemental magnesium but is often less well absorbed and more likely to cause diarrhea. Citrate and glycinate are often chosen when tolerability matters, though product quality and dose still matter.
Safety and interactions
Magnesium from food is generally safe for healthy people because the kidneys remove excess amounts. Supplements and magnesium-containing medicines can cause side effects, most commonly diarrhea, nausea, and abdominal cramping. Very high intakes from supplements or medicines can lead to hypermagnesemia, especially in people with kidney disease.
Symptoms of too much magnesium can include lethargy, low blood pressure, flushing, nausea, muscle weakness, and in severe cases dangerous heart rhythm problems or cardiac arrest. Risk is much higher if kidney function is reduced because the body cannot clear magnesium effectively.
Important interactions include:
- Antibiotics: Magnesium can reduce absorption of tetracyclines and fluoroquinolones.
- Bisphosphonates: It can reduce absorption of osteoporosis medicines such as alendronate.
- Levothyroxine: Magnesium can interfere with thyroid hormone absorption.
- Diuretics and proton pump inhibitors: These can lower magnesium levels over time.
Because timing matters, people taking these medicines should ask a clinician or pharmacist how to separate doses. Anyone with kidney disease, heart rhythm problems, or multiple medicines should not start high-dose magnesium without medical advice.
When to see a clinician
See a clinician if you have symptoms that could suggest magnesium deficiency, such as persistent muscle cramps, tremor, weakness, palpitations, or seizures. Medical review is also important if you have chronic vomiting or diarrhea, poorly controlled diabetes, alcohol use disorder, or long-term use of medicines known to lower magnesium.
Seek urgent care for fainting, severe weakness, confusion, chest symptoms, or suspected abnormal heart rhythm. If you have kidney disease, do not self-treat with magnesium supplements or laxatives unless a clinician says they are safe for you.
Limitations and open questions
Magnesium is biologically important, but measuring magnesium status is not straightforward. Serum magnesium is the most common test, and a normal result does not always rule out low total body magnesium because less than 1% of magnesium is in blood. More specialized tests exist, but they are not routinely used in most clinical settings.
Research on magnesium supplements for chronic conditions is still evolving. Many studies are small, use different magnesium salts and doses, or include people with different baseline magnesium status, which makes results hard to compare. Evidence is strongest for correcting deficiency and weaker for broad claims about sleep, mood, exercise recovery, or disease prevention.
Another open question is how much low magnesium intake contributes to population health problems compared with other dietary factors. Public health approaches that improve overall diet quality may matter more than routine supplementation for most healthy adults. For individual decisions, the key questions are whether intake is low, whether symptoms or lab abnormalities suggest deficiency, and whether kidney function and medicines make supplementation risky.
FAQs
What does magnesium do in the body?
Magnesium helps run more than 300 enzyme systems involved in energy production, muscle contraction, nerve signaling, and blood pressure regulation. It also supports DNA and RNA synthesis and helps maintain normal heart rhythm. About 50% to 60% of the body's magnesium is stored in bone.
What foods are high in magnesium?
Good sources include nuts, seeds, legumes, whole grains, and green leafy vegetables. Examples are pumpkin seeds, almonds, peanuts, beans, oats, brown rice, and spinach. In Indian diets, dals, chana, rajma, sesame seeds, groundnuts, ragi, and other millets can add meaningful magnesium.
How do I know if I have low magnesium?
Low magnesium can cause muscle cramps, weakness, tremor, palpitations, seizures, or abnormal blood levels of potassium and calcium. A serum magnesium test is commonly used, and hypomagnesemia is often defined as less than 0.75 mmol/L. But because less than 1% of body magnesium is in blood, a normal serum level does not always exclude low body stores.
Are magnesium supplements safe?
They are often safe in appropriate amounts for people with normal kidney function, but diarrhea, nausea, and abdominal cramping are common side effects. Risk is higher with large doses and in people with kidney disease, because excess magnesium can build up. Magnesium can also interact with antibiotics, bisphosphonates, and levothyroxine, so it is worth checking with a clinician or pharmacist.
Which form of magnesium supplement is best?
There is no single best form for everyone. Magnesium oxide provides a lot of elemental magnesium but is often less well absorbed and more likely to cause diarrhea, while citrate and glycinate are often chosen for better tolerability. The right choice depends on why it is being used, other medicines, kidney function, and how much elemental magnesium the product contains.