Most adults need between 310 and 420 mg of magnesium per day, depending on age and sex. Men generally need more than women, and the recommendation increases slightly after age 30. If you’re pregnant, your needs go up as well.
Daily Recommendations by Age and Sex
The National Institutes of Health sets these Recommended Dietary Allowances for magnesium:
- Children 1–3 years: 80 mg
- Children 4–8 years: 130 mg
- Children 9–13 years: 240 mg
- Teen boys 14–18: 410 mg
- Teen girls 14–18: 360 mg
- Men 19–30: 400 mg
- Women 19–30: 310 mg
- Men 31 and older: 420 mg
- Women 31 and older: 320 mg
- Pregnant women: 350–360 mg (varies by age)
For infants under one year, there isn’t enough data to set a formal RDA. Instead, the guideline is an “adequate intake” of 30 mg for newborns up to 6 months and 75 mg from 7 to 12 months, amounts typically covered by breast milk or formula.
Food Sources vs. Supplements
The RDA refers to your total magnesium intake from all sources: food, drinks, and supplements combined. Many people can hit their target through diet alone. Nuts are among the richest sources, with a single ounce of almonds or cashews providing roughly 75–80 mg. Pumpkin seeds are even higher. Cooked spinach, black beans, edamame, and whole grains like brown rice and oatmeal all contribute meaningful amounts. Dark chocolate is another surprisingly good source, offering about 65 mg per ounce.
That said, surveys consistently show that a large portion of the population falls short of the RDA through food alone, especially older adults and people who eat a highly processed diet. If your meals lean heavily on refined grains, fast food, and few vegetables, you’re more likely to come up short.
Supplement Safety and Upper Limits
Magnesium from food is not associated with any risk of overdose in healthy people, because your kidneys efficiently clear any excess. Supplements are a different story. The tolerable upper intake level for supplemental magnesium (meaning magnesium from pills, powders, or liquids, not food) is 350 mg per day for adults. Going above that doesn’t guarantee problems, but it increases the chance of digestive side effects like diarrhea, nausea, and cramping.
This is an important distinction that confuses a lot of people: the RDA for an adult man is 420 mg total, but the safe upper limit for supplements alone is 350 mg. That’s because the rest is expected to come from food. If you’re already eating a reasonably balanced diet, a supplement in the range of 200–350 mg is typically enough to close any gap.
What Happens When You Get Too Little
Mild magnesium shortfalls often fly under the radar for a while. Early signs tend to be vague: loss of appetite, fatigue, general weakness, and nausea. As a deficiency deepens, more noticeable symptoms show up, including muscle cramps, numbness or tingling in the hands and feet, and irregular heartbeat. In severe cases, which are uncommon in otherwise healthy people, seizures can occur.
Certain groups face higher risk. People with digestive conditions like Crohn’s disease or celiac disease absorb less magnesium from food. Type 2 diabetes, chronic alcohol use, and long-term use of certain medications (particularly proton pump inhibitors for acid reflux) can all deplete magnesium levels over time. Older adults absorb less magnesium from the gut and tend to excrete more of it through the kidneys, which is why deficiency becomes more common with age.
What Happens When You Get Too Much
Magnesium toxicity, called hypermagnesemia, is rare in people with healthy kidneys. Your body is quite good at flushing excess magnesium through urine. The real risk comes from taking very large supplement doses or using magnesium-containing laxatives and antacids frequently, especially if you have kidney disease that limits your ability to clear it.
Mild excess may cause low blood pressure that doesn’t respond well to treatment. Moderate to severe cases can bring dizziness, confusion, difficulty breathing, and muscle weakness. At dangerously high levels, magnesium can cause paralysis, abnormal heart rhythms, and cardiac arrest. These extreme outcomes are almost exclusively seen in people with kidney failure or those who ingest massive amounts of magnesium-containing products like Epsom salts.
Choosing a Supplement Form
Not all magnesium supplements are created equal. The form of magnesium determines how well your body absorbs it and what you’re likely to feel.
Magnesium citrate is one of the most bioavailable forms, meaning your digestive tract absorbs a higher percentage of each dose. It’s widely available and affordable, though it can have a mild laxative effect, which some people consider a bonus and others find inconvenient. Magnesium glycinate is also well absorbed and tends to be gentler on the stomach, making it a popular choice for people who are sensitive to digestive side effects. Magnesium malate absorbs well too and is often marketed toward people looking for energy and muscle support.
Magnesium oxide is one of the most common forms on store shelves because it’s cheap and packs a lot of elemental magnesium per pill. The trade-off is that it’s poorly absorbed compared to other forms, so a 500 mg capsule of magnesium oxide delivers far less usable magnesium than the label might suggest. Magnesium chloride and magnesium lactate both absorb well and are solid middle-ground options.
Magnesium L-threonate has gained attention for brain health, as it appears to cross the blood-brain barrier more effectively, though it contains less elemental magnesium per dose. If your goal is better sleep, Cleveland Clinic recommends about 200 mg of magnesium taken 30 minutes before bed.
Practical Tips for Getting Enough
If you’re trying to reach your daily target, start by looking at your diet before reaching for a supplement. A breakfast of oatmeal with a handful of almonds gets you roughly 120–130 mg before lunch. Add a cup of cooked spinach or black beans at dinner and you’re well past the halfway mark. Snacking on pumpkin seeds, choosing whole grains over refined ones, and including legumes a few times a week can close most of the gap for most people.
If you do supplement, take your dose with food to improve absorption and reduce the chance of stomach upset. Splitting a larger dose into two smaller ones (morning and evening) can also help with absorption and minimize digestive issues. And pay attention to the “elemental magnesium” listed on the supplement label, not just the total weight of the compound. A capsule labeled “magnesium glycinate 500 mg” may contain only 70–100 mg of actual magnesium. The elemental amount is what counts toward your daily target.