Magnesium is a mineral involved in hundreds of body processes, including muscle and nerve function, heart rhythm and bone strength. Most people can meet their needs through food, but some groups fall short, and too much from supplements can cause digestive problems. This guide covers daily needs, food sources, deficiency signs, safe limits and medicine interactions, based on the NIH Office of Dietary Supplements consumer fact sheet.
How Much Magnesium Do You Need Each Day?
The NIH lists these average daily amounts from all sources:
- Children 1 to 3 years: 80 mg
- Children 4 to 8 years: 130 mg
- Children 9 to 13 years: 240 mg
- Teen boys 14 to 18 years: 410 mg; teen girls 14 to 18 years: 360 mg
- Adult men: 400 to 420 mg, depending on age
- Adult women: 310 to 320 mg, depending on age
- Pregnant women: 350 to 360 mg (400 mg for pregnant teens)
- Breastfeeding women: 310 to 320 mg (360 mg for breastfeeding teens)
Best Food Sources of Magnesium
Magnesium found naturally in food is not harmful, so there is no upper limit for food sources.
- Legumes such as beans, lentils and peas
- Nuts and seeds
- Whole grains
- Green leafy vegetables such as spinach
- Fortified breakfast cereals and other fortified foods
- Milk, yogurt and some other milk products
Who Is Likely to Get Too Little Magnesium?
The NIH says men older than 70 and teenage boys and girls are most likely to have low intakes. Others at higher risk of low magnesium include:
- People with digestive diseases such as Crohn disease and celiac disease
- People with type 2 diabetes
- People with long-term alcoholism
- Older adults
Signs of Magnesium Deficiency
Short-term low intake usually causes no obvious symptoms. Over time, symptoms can include loss of appetite, nausea, vomiting, fatigue and weakness. Extreme deficiency can cause numbness, tingling, muscle cramps, seizures, personality changes and abnormal heart rhythm. These symptoms have many other possible causes, so see a doctor rather than self-diagnosing.
Magnesium Supplements: Forms and Upper Limit
Magnesium aspartate, citrate, lactate and chloride are absorbed more easily. Magnesium is also found in some laxatives and in some heartburn and indigestion products.
The upper limit applies to supplements and medicines only, not to food:
- Children 1 to 3 years: 65 mg
- Children 4 to 8 years: 110 mg
- Children 9 to 18 years and adults: 350 mg
Taking more than the upper limit from supplements can cause diarrhea, nausea and abdominal cramping. Extremely high intakes can cause irregular heartbeat and cardiac arrest.
Magnesium and Medicine Interactions
- Bisphosphonates used for osteoporosis may not be absorbed well if taken too close in time to high-magnesium products.
- Antibiotics may not be absorbed if taken too soon before or after a magnesium supplement.
- Diuretics can increase or decrease magnesium loss in the urine, depending on the type.
- Long-term use of prescription medicines for acid reflux or ulcers can lower blood magnesium.
- Very high doses of zinc supplements can interfere with magnesium absorption.
Ask your doctor or pharmacist how to space supplements and medicines. You can also read our guide to zinc daily needs and safe limits.
When to See a Doctor
- You have ongoing muscle cramps, numbness or tingling
- You have a digestive condition, diabetes or take long-term acid reflux medicine
- You are thinking of taking a magnesium supplement every day
- You take other medicines that may interact
Frequently Asked Questions
How much magnesium do adults need per day?
Adult men need 400 to 420 mg and adult women need 310 to 320 mg a day, depending on age, according to the NIH.
Which foods are high in magnesium?
Legumes, nuts, seeds, whole grains, green leafy vegetables such as spinach, fortified cereals, milk and yogurt are good sources.
What is the upper limit for magnesium supplements?
For adults and children 9 and older, the upper limit from supplements and medicines is 350 mg a day. It does not apply to magnesium from food.
What are the signs of too much magnesium from supplements?
Diarrhea, nausea and abdominal cramping. Extremely high intakes can cause irregular heartbeat.
Can magnesium interact with medicines?
Yes. It can affect how well bisphosphonates and some antibiotics are absorbed, so ask your doctor or pharmacist how to time your doses.
Related reading: Zinc daily needs and safe limits | Calcium daily needs and supplements | Vitamin D daily needs and sources
Sources
- NIH Office of Dietary Supplements: Magnesium fact sheet for consumers
- NIH Office of Dietary Supplements: Zinc fact sheet for consumers
Medical disclaimer: this article is for general information and does not replace advice from a qualified doctor. Do not start, stop or change any supplement or medicine without medical advice.