Most adults need between 310 and 420 mg of magnesium per day, depending on age and sex. Men generally need more than women, and pregnancy increases the requirement. These numbers come from the Recommended Dietary Allowances set by the National Academies of Sciences, Engineering, and Medicine.
Daily Requirements by Age and Sex
Magnesium needs climb throughout childhood and peak in adolescence, then settle into adult ranges that differ between men and women. Here are the current recommendations for adults:
- Men 19 to 30: 400 mg
- Men 31 and older: 420 mg
- Women 19 to 30: 310 mg
- Women 31 and older: 320 mg
- Pregnant women 19 to 30: 350 mg
- Pregnant women 31 to 50: 360 mg
- Breastfeeding women: 310 to 320 mg
Children and teens need less, ranging from 80 mg for toddlers (ages 1 to 3) up to 410 mg for teenage boys (ages 14 to 18). Teenage girls need about 360 mg. Infants under one year have an adequate intake set at 30 to 75 mg, which is typically met through breast milk or formula.
Athletes May Need More
If you exercise intensely, your magnesium needs are likely higher than average. Strenuous exercise increases magnesium losses through both urine and sweat, and research estimates this can raise requirements by 10 to 20% above the standard recommendation. For a man already targeting 420 mg, that could mean needing closer to 460 to 500 mg per day.
Dietary surveys of athletes suggest that intakes below 260 mg for men and 220 mg for women are associated with deficient magnesium status. If you train hard and eat a restricted diet, paying attention to magnesium-rich foods becomes especially important.
Best Food Sources
Magnesium is found in a wide range of whole foods, and most people can meet their daily needs through diet alone. The richest sources are seeds, nuts, leafy greens, and whole grains. A quarter cup of pumpkin seeds delivers roughly 150 mg. An ounce of almonds provides around 80 mg. A cup of cooked spinach contains about 157 mg, and a half cup of black beans offers around 60 mg. Dark chocolate, avocados, and whole wheat bread also contribute meaningful amounts.
One thing to be aware of: phytic acid, a compound found naturally in whole grains, legumes, and seeds, can bind to magnesium and reduce how much your body absorbs. This doesn’t mean you should avoid these foods (they’re some of the best magnesium sources available), but it does mean that the magnesium listed on a nutrition label isn’t the exact amount your body takes in. Soaking, sprouting, or fermenting grains and legumes can reduce phytic acid content and improve mineral absorption.
Choosing a Supplement
If you’re considering a supplement, the form of magnesium matters. Organic forms like magnesium citrate and magnesium glycinate dissolve more easily and are absorbed better than inorganic forms like magnesium oxide. Magnesium oxide packs more elemental magnesium per pill, but your body uses a smaller fraction of it. Studies testing commercially available magnesium products have found wide variation in how well different formulations dissolve and get absorbed, so the label dose and the effective dose aren’t always the same.
The tolerable upper intake level for supplemental magnesium is 350 mg per day for adults. This cap applies only to magnesium from supplements and medications, not from food. You cannot get too much magnesium from food alone. Exceeding 350 mg from supplements is where side effects start to appear, most commonly diarrhea and stomach cramps. Magnesium’s laxative effect is, in fact, the reason it’s used in many over-the-counter laxative products.
Signs You’re Not Getting Enough
Mild magnesium deficiency often shows up as nausea, loss of appetite, fatigue, and general weakness. These symptoms are vague enough that many people chalk them up to stress or poor sleep without considering their mineral intake. As deficiency worsens, the signs become more distinctive: muscle cramps, spasms, tremors, and tingling or numbness. Normal blood magnesium levels fall between 1.46 and 2.68 mg/dL, though blood tests can miss a subtle shortfall because most of your body’s magnesium is stored in bones and tissues, not in the bloodstream.
Severe deficiency is uncommon in otherwise healthy people but can cause seizures and dangerous heart rhythm changes. Certain conditions increase risk, including chronic alcohol use, type 2 diabetes, and digestive disorders that impair nutrient absorption.
Too Much Magnesium: What Happens
Magnesium toxicity from food is essentially impossible because your kidneys efficiently filter out any excess. The risk comes from high-dose supplements or magnesium-containing medications, particularly in people with reduced kidney function.
Mild excess typically causes loose stools and digestive discomfort. At higher levels, symptoms can include low blood pressure, dizziness, nausea, confusion, and muscle weakness. In rare and extreme cases, very high magnesium levels can lead to difficulty breathing, dangerously slow heartbeat, and cardiac arrest. These severe outcomes are almost always tied to intravenous magnesium or massive oral doses in someone whose kidneys can’t clear the mineral normally.
Magnesium for Sleep and Migraines
Beyond meeting your baseline requirement, some people take higher doses of magnesium for specific health goals. Sleep is the most common reason. Clinical studies on magnesium and sleep have used doses ranging from 250 to 729 mg, typically as magnesium oxide or magnesium glycinate, taken for several weeks to months. Some trials have shown improvements in slow-wave sleep (the deepest, most restorative phase) in older adults, while others found no significant benefit. Results have been inconsistent, and the best dose for sleep hasn’t been firmly established.
For migraine prevention, magnesium has a longer track record. Pediatric studies have used doses of 4 to 6 mg per kilogram of body weight daily. For adults, many neurologists recommend 400 to 500 mg of magnesium per day as a preventive measure, though this exceeds the supplement upper limit and should be discussed with a healthcare provider. Magnesium citrate or glycinate are generally preferred over oxide for this purpose because of better absorption.