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How Much Magnesium Do You Need per Day?
How much magnesium per day depends on age and sex: adult men need 400-420 mg and adult women 310-320 mg, counting food and drink. A separate upper limit of 350 mg applies to magnesium from supplements and medicines alone. One Synaptril capsule has 80 mg of magnesium, well under both numbers.
Written by the Synaptril label deskUpdated · 4 min read
How much magnesium do adults need per day?
Adult men need 400-420 mg of magnesium a day and adult women need 310-320 mg. These are the Recommended Dietary Allowances, and they count magnesium from everything you eat and drink (NIH ODS, Magnesium).
The NIH Office of Dietary Supplements sets them. The exact figure inside each range depends on age.
What is the upper limit for magnesium supplements?
For adults, magnesium from supplements and medicines has an upper limit of 350 mg a day. Magnesium that comes naturally in food does not count toward it (NIH ODS, Magnesium).
The limit exists because supplemental magnesium commonly causes diarrhea, nausea and cramping at high doses. Very high doses can cause low blood pressure and an irregular heartbeat (NIH ODS, Magnesium).
| Number | Amount | What it covers |
|---|---|---|
| RDA, men | 400-420 mg | Food plus supplements |
| RDA, women | 310-320 mg | Food plus supplements |
| Supplement limit | 350 mg | Supplements and medicines only |
| One Synaptril capsule | 80 mg (19% DV) | Supplement |
How does 80 mg of magnesium fit alongside food?
Eighty mg leaves 270 mg of room under the 350 mg supplement limit. The label prints 19% of the Daily Value, so the capsule is a small top-up, not a full day's magnesium.
Add up every product before you stack. A multivitamin, an antacid or a sleep aid may carry magnesium too, and the sum from supplements is what the limit measures.
Blend math adds one point: the 80 mg is elemental magnesium, and it needs about 567 mg of magnesium glycinate, almost the whole 575 mg blend (GlobalRPH, Magnesium Glycinate).
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See packsWhat does a worked magnesium day look like?
A worked day adds food, then supplements, then checks each total against its own number. Take a woman with a 320 mg RDA who takes one Synaptril capsule.
The capsule supplies 80 mg, which is 25% of 320 mg. Food then covers the remaining 240 mg. Her supplement total is 80 mg, which sits 270 mg under the 350 mg limit (NIH ODS, Magnesium).
Now add a second product with 200 mg of magnesium. The supplement total becomes 280 mg, still under the limit but with less room. A third product could push it over, so count each label.
The bar shows where the 80 mg sits inside the 575 mg blend.
Who needs to watch their magnesium intake?
People on certain medicines should watch their magnesium. Magnesium can reduce absorption of bisphosphonates and bind tetracycline and quinolone antibiotics, and water pills or long-term acid reducers change magnesium levels (NIH ODS, Magnesium).
Ask a doctor or pharmacist about timing and keep taking prescribed medicine. The Synaptril label also asks you to consult a physician if you take a medication or have a condition.
Order Synaptril on the official checkout
Order-page prices, October 18, 2026 (Synaptril sales page). The 2-bottle pack is $178 plus shipping. Every pack has the 60-day money-back guarantee. Compare all packs.
Related: magnesium glycinate, supplement facts and magnesium glycinate side effects.
FAQ01
Synaptril questions people ask
Does the 350 mg limit include magnesium from food?
No. The 350 mg upper limit counts only magnesium from supplements and medicines. Magnesium that comes naturally in food and drink counts toward the RDA but not toward that limit.
Can you get enough magnesium from food alone?
Many people can, since the RDA counts food. Our sources do not rank foods, so check your own intake with a dietitian if you are unsure.
Is 80 mg of magnesium too little to matter?
It is 19% of the Daily Value, so it adds a real but small share. It is not a full daily dose, and no study has shown that this amount changes memory or focus.
Who wrote this02
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