Blog · Safety
How Much Magnesium Is Too Much? The 350 mg Line Explained
How much magnesium is too much depends on the source. The upper limit for magnesium from supplements is 350 mg a day for adults, and loose stools are the first sign you passed it. Food magnesium does not count toward that limit. Synaptril holds 80 mg per capsule, one capsule a day, which sits well below the line.
Written by the Synaptril label deskUpdated · 4 min read
The number01
What is the upper limit for magnesium?
The upper limit for magnesium from supplements and medicines is 350 mg a day for adults. The Office of Dietary Supplements sets it because larger doses can cause diarrhea and cramps (NIH ODS, Magnesium).
The limit covers added magnesium only. Magnesium in food, such as nuts, beans and greens, is not counted, because the gut manages food amounts well.
For a worked example, one capsule gives 80 mg. Add a 200 mg magnesium tablet and you reach 280 mg, still under the line. Add a second tablet and you pass it. Small doses stack fast.
The daily need from all sources is 400 to 420 mg for men and 310 to 320 mg for women. So the limit and the need are two different numbers. Eating enough does not put you near the limit.
Bars02
Where does Synaptril's 80 mg sit?
Synaptril's 80 mg is about 23% of the 350 mg supplement limit and 19% of the daily value on the label. One capsule a day leaves wide room.
The bars below set the 80 mg against the recommended intake, and show the other blend lines with their label-order ceilings.
| Measure | Amount per day |
|---|---|
| Synaptril, one capsule | 80 mg (19% DV) |
| Upper limit, supplements only | 350 mg |
| Need for women, all sources | 310 to 320 mg |
| Need for men, all sources | 400 to 420 mg |
Ceilings and estimates for the other lines come from label order rules (21 CFR 101.36, supplement labeling). They are not lab results.
Signs03
What are the signs of too much magnesium?
The first sign of too much magnesium is loose stool or diarrhea, often with cramps and nausea. It usually settles when the dose drops (NIH ODS, Magnesium).
Very high intakes, mostly from laxatives or antacids, can cause low blood pressure, a slow heartbeat, confusion and breathing trouble. These are rare in healthy adults, but they are an emergency. Call 911 or local emergency services for them.
Common and mild
Loose stools, cramps, nausea. Cut back and ask a physician if it continues.
Rare and urgent
Slow pulse, faint feeling, confusion, trouble breathing. Get emergency care.
Synaptril: from $49 a bottle30 capsules · 2, 3 or 6 bottles · free shipping on 3 or 6 · 60-day money-back guarantee
See packsWho should be careful04
Who should be careful with magnesium supplements?
People with kidney disease should be careful with magnesium supplements, because weak kidneys clear the mineral slowly and levels can build up (NIH ODS, Magnesium).
Ask a physician first if you take antibiotics, bone drugs, diuretics or acid reducers. Synaptril is not for anyone under 18 or pregnant or nursing, and it should not exceed one capsule a day.
Add up every magnesium source before you add a capsule: a multivitamin, an antacid, a sleep product. Several small doses can total more than you think. Keep taking prescribed medicine, and see our Synaptril side effects page for the full list.
American Synaptril authorized shop
Ready to try Synaptril?
Start with a medicine check, then choose your pack. Three or six bottles cost less per bottle and ship free, and each pack comes with the 60-day money-back guarantee.
- Secure checkout
- 60-day money-back guarantee
- Ships from the U.S.
FAQ05
Magnesium limit questions
Can you overdose on magnesium from food?
It is very unlikely. The gut and kidneys handle food magnesium well, which is why the 350 mg limit covers supplements and medicines only (NIH ODS, Magnesium). Trouble comes from concentrated products, especially laxatives and antacids taken often.
Is 400 mg of magnesium a day too much?
It depends on the source. 400 mg from food is normal, since it matches the daily need for men. 400 mg from supplements is above the 350 mg limit and may cause loose stools. Ask a physician before going there.
What should I do if magnesium gives me diarrhea?
Lower the dose or pause the product, and drink fluids. Check other magnesium sources, such as antacids, that may be adding up. If loose stools last more than a few days, ask a physician.
Does taking two Synaptril capsules double the risk?
It doubles the magnesium to 160 mg and every blend line too, which the label forbids. The label says not to exceed the recommended dose. Two capsules would still sit under 350 mg but the other ingredients are unknown.
Does magnesium from antacids count toward the limit?
Yes. Antacids and laxatives that contain magnesium are medicines, so their magnesium counts toward the 350 mg limit (NIH ODS, Magnesium). Read the active ingredient list on any antacid, and add it to your capsule total before you decide.
Who wrote this06
Written and reviewed by
Pages built from the label, the sales page and linked NIH, FDA, CDC, FTC and peer-reviewed sources.
Last updated . Read our editorial standards and how we check reviews. This website is run by an American Synaptril authorized shop, not by the manufacturer or the distributor. We earn money when you buy through our order links.
Keep reading
More about Synaptril
American Synaptril authorized shop
Ready to try Synaptril?
Start with a medicine check, then choose your pack. Three or six bottles cost less per bottle and ship free, and each pack comes with the 60-day money-back guarantee.
- Secure checkout
- 60-day money-back guarantee
- Ships from the U.S.