Magnesium: what it does, how much you need, and how much is too much
By Vita · fact-checked against NIH ODS
Vita is Vitaminico's AI nutrition coach. Every number here is checked against the NIH Office of Dietary Supplements; these pages have not yet been reviewed by our registered dietitians.
A mineral your body uses in 300+ enzyme reactions for muscle, nerve and energy function
Magnesium: key facts
- Everyday need (RDA/AI)
- 400-420 mg for men (400 at 19-30, 420 at 31+); 310-320 mg for women (310 at 19-30, 320 at 31+)
- Safe upper limit (UL)
- 350 mg (supplemental only)
- Measured in
- mg
- Best foods
- Pumpkin and chia seeds, almonds and other nuts, spinach and green leafy vegetables, legumes, whole grains
Adult values from the NIH ODS Magnesium fact sheet. Needs differ in pregnancy, lactation and childhood.
What does magnesium do?
Magnesium is a cofactor in more than 300 enzyme systems that regulate muscle and nerve function, blood sugar control, blood pressure, and energy production. It helps build bone, make DNA and proteins, and move calcium and potassium across cell membranes, which keeps your heart rhythm steady and your muscles contracting normally. Your body holds about 25 grams of magnesium, with 50–60% stored in your bones.
Why you might be low on magnesium
- Gut conditions like Crohn's disease or celiac disease, or intestinal surgery, that reduce how much magnesium you absorb
- Type 2 diabetes, which raises the amount of magnesium lost in urine
- Regular heavy alcohol use, which is a common cause of magnesium deficiency
- Being an older adult — intake drops, gut absorption falls, and the kidneys excrete more with age
- A diet low in leafy greens, nuts, seeds, beans and whole grains; refining and processing grains strips out most of their magnesium
Signs of low magnesium
These are common signals, not a diagnosis — a blood test and your clinician confirm a real gap.
- Loss of appetite, nausea or vomiting
- Fatigue and weakness
- Numbness and tingling
- Muscle cramps and contractions
- Abnormal heart rhythms
- In severe cases, seizures or low blood calcium or potassium
Best food sources of magnesium
| Food | Typical amount |
|---|---|
| Pumpkin seeds, roasted | 156 mg per 1 ounce |
| Chia seeds | 111 mg per 1 ounce |
| Almonds, dry roasted | 80 mg per 1 ounce |
| Spinach, boiled | 78 mg per ½ cup |
| Black beans, cooked | 60 mg per ½ cup |
| Peanut butter, smooth | 49 mg per 2 tablespoons |
| Brown rice, cooked | 42 mg per ½ cup |
How much magnesium is too much?
The tolerable upper intake level (UL) for adults is 350 mg (supplemental only) per day. The 350 mg UL applies only to supplements and medications, not magnesium naturally in food; high supplemental doses cause diarrhea, while food magnesium poses no toxicity risk.
Magnesium naturally in food isn't a concern because healthy kidneys clear the excess, but high doses from supplements or magnesium-based laxatives and antacids can cause diarrhea, nausea and abdominal cramping — the upper limit from supplements alone is 350 mg a day for adults. Very high doses can lead to magnesium toxicity, causing low blood pressure, irregular heartbeat and, rarely, cardiac arrest, with the risk greatest for people who have reduced kidney function.
Stacking a multivitamin, a single supplement and fortified foods adds up faster than it looks — run your full dose through the free Supplement Safety Checker before adding anything new.
Magnesium FAQ
Do I need a magnesium supplement?
Many people in the U.S. get less than the recommended amount, but symptomatic deficiency is uncommon in healthy people because the kidneys conserve magnesium. A diet with greens, nuts, seeds, beans and whole grains usually covers the roughly 310–420 mg adults need each day.
Which form of magnesium absorbs best?
Forms that dissolve well in liquid — such as magnesium citrate, lactate, aspartate and chloride — tend to be absorbed better than magnesium oxide or magnesium sulfate.
Can magnesium interfere with my medications?
Yes. Magnesium can reduce absorption of some osteoporosis drugs (bisphosphonates like alendronate) and certain antibiotics (tetracyclines and quinolones), so take those at least 2 hours apart. Some diuretics and proton pump inhibitors can also change your magnesium levels.
Source
Every RDA/AI, upper limit and unit on this page is drawn from the NIH Office of Dietary Supplements Magnesium fact sheet ›.
Vitaminico for iPhone
Not sure if magnesium is your gap?
- A free 2-minute chat with Vita reads your symptoms — no food-logging, no needles
- Get your top 3 likely nutrient gaps across the vitamins and minerals that matter
- A food-first plan: what to eat, where to get it, and what to skip
- No signup wall — the full check works the moment you open the app
Free · iPhone · no email to start
Educational, not medical advice. The upper limits shown are Tolerable Upper Intake Levels for healthy adults from all sources combined; needs differ in pregnancy, lactation, childhood and with some conditions or medications. This page does not diagnose a deficiency or set your dose — talk to your clinician before starting any high-dose supplement.