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How Much Magnesium Per Day Do Adults Need?
How much magnesium per day adults need depends on age and sex. NIH sets the Recommended Dietary Allowance at 310 to 420 mg. The upper limit from supplements alone is 350 mg. One Synaptril capsule has 80 mg of magnesium, about 19% of the Daily Value.
Written by the Synaptril label deskUpdated · 4 min read
The targets01
How much magnesium do adults need each day?
Adults need 310 to 420 mg of magnesium a day, depending on age and sex. NIH lists the exact numbers (NIH ODS, Magnesium).
These totals count food and drink as well as pills. Most people get a large part from meals.
| Group | mg a day |
|---|---|
| Men 19 to 30 | 400 |
| Men 31 and older | 420 |
| Women 19 to 30 | 310 |
| Women 31 and older | 320 |
Source: NIH Office of Dietary Supplements (NIH ODS, Magnesium).
The ceiling02
What is the upper limit for magnesium supplements?
The upper limit for magnesium from supplements is 350 mg a day for adults. NIH applies this to supplements and medicines, not to food (NIH ODS, Magnesium).
Above that, diarrhea, nausea and abdominal cramps become common. Poor kidney function raises the risk of toxicity (NIH ODS, Magnesium).
The limit is a ceiling, not a goal. Most people do not need to approach it.
Worked example03
How does 80 mg of magnesium fit in?
One Synaptril capsule gives 80 mg of magnesium, as magnesium glycinate. That is 19% of the label's Daily Value.
Take a woman aged 35 whose target is 320 mg. The capsule covers 25% of it. For a man of 35 at 420 mg, it covers about 19%.
- 80 mg is 23% of the 350 mg supplement limit.
- If you add a second magnesium product, add the elemental amounts together.
- Food still supplies most of your day.
The full panel is in the Supplement Facts breakdown.
Synaptril: from $49 a bottle30 capsules · 2, 3 or 6 bottles · free shipping on 3 or 6 · 60-day guarantee
See packsSafety04
Who should check before taking magnesium?
People with kidney disease and people on certain medicines should check with a doctor first. The Synaptril label also says to consult a physician if you take medication or have a medical condition.
Magnesium can lower absorption of bisphosphonates and of tetracycline and quinolone antibiotics, so timing matters (NIH ODS, Magnesium). Diuretics and long use of acid reducers affect magnesium levels (NIH ODS, Magnesium).
Never stop or change a prescription because of a supplement. Ask a pharmacist how to space them.
The bottle05
Does one capsule a day meet your magnesium needs?
No. One capsule supplies a fraction of daily needs, and the label makes no claim that it replaces food.
The directions say to take one capsule daily. See how to use Synaptril for the full steps.
FAQ06
Daily magnesium questions
Is 400 mg of magnesium a day too much?
It can be, as a supplement. NIH sets 350 mg a day from supplements as the upper level, though food magnesium does not count toward it (NIH ODS, Magnesium). Total intake from food can reach 400 mg without trouble for many men.
What percent of the daily value is one Synaptril capsule?
The label prints 80 mg of magnesium as 19% of the Daily Value. Against NIH targets, it is about 19% for a man of 31 or older and 25% for a woman of 31 or older (NIH ODS, Magnesium).
Do men and women need different amounts?
Yes. NIH lists 400 mg for men 19 to 30 and 420 mg for men 31 and older. Women need 310 mg at ages 19 to 30 and 320 mg at 31 and older (NIH ODS, Magnesium).
What happens if you take too much magnesium?
Diarrhea, nausea and abdominal cramps are the common effects of high supplemental doses. NIH also warns that poor kidney function raises the risk of toxicity (NIH ODS, Magnesium). Stop and call a provider if you feel unwell.
Does magnesium from food count toward the 350 mg limit?
No. NIH applies the 350 mg upper level to magnesium from supplements and medicines only, not from food (NIH ODS, Magnesium). That is why a person can eat more than 350 mg in a day without reaching the limit.
Can I take Synaptril with an antibiotic?
Ask first. NIH says magnesium can reduce absorption of tetracycline and quinolone antibiotics, so take the antibiotic at least 2 hours before or 4 to 6 hours after (NIH ODS, Magnesium). Your pharmacist can plan the timing.
Who wrote this07
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Last updated . See our editorial standards and how we check reviews. This website is run by Getsynaptril, a stocked U.S. Synaptril counter, not by the manufacturer or the distributor. We are paid when you buy through our order links.
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