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What Are the Side Effects of Magnesium Glycinate?
Magnesium glycinate side effects are mostly digestive: diarrhea, nausea and abdominal cramping, and they grow with the dose. Magnesium also interacts with some antibiotics and osteoporosis drugs, and people with kidney disease should ask a doctor first. One Synaptril capsule has 80 mg, far below the 350 mg supplement limit.
Written by the Synaptril label deskUpdated · 4 min read
What are the most common magnesium glycinate side effects?
The most common side effects of magnesium supplements are diarrhea, nausea and abdominal cramping. They happen mainly at high doses (NIH ODS, Magnesium).
Very high doses can cause low blood pressure, an irregular heartbeat and, in the extreme, cardiac arrest (NIH ODS, Magnesium). That range is far above the 80 mg in a Synaptril capsule.
We found no source that ranks glycinate against other forms for stomach effects, so we make no such claim.
Does the dose change the side effects?
Yes, dose is the main driver. The supplement limit is 350 mg a day, and the NIH ties digestive effects to high supplemental doses (NIH ODS, Magnesium).
| Level | What the source says |
|---|---|
| One capsule, 80 mg | 19% of the Daily Value; under the limit |
| Up to 350 mg from supplements | Within the upper limit |
| High supplemental doses | Diarrhea, nausea, cramping |
| Very high doses | Low blood pressure, irregular heartbeat |
If a capsule upsets your stomach, tell your provider and stop until you have spoken. Problems can be reported to FDA (FDA, How to Report a Problem).
Which medicines interact with magnesium glycinate?
Magnesium interacts with osteoporosis drugs, some antibiotics, water pills and long-term acid reducers (NIH ODS, Magnesium).
- Bisphosphonates: separate from magnesium by at least 2 hours.
- Tetracycline and quinolone antibiotics: take the antibiotic at least 2 hours before or 4-6 hours after magnesium.
- Loop and thiazide diuretics: they increase magnesium loss.
- Proton pump inhibitors over a year: can lower magnesium.
Keep taking prescribed medicine and change nothing without your prescriber.
Synaptril: from $49 a bottle30 capsules · 2, 3 or 6 bottles · free shipping on 3 or 6 · 60-day guarantee
See packsHow can you check your own medicine against magnesium?
Pick your medicine type and the tool below shows which Synaptril ingredient matters for it. Magnesium comes up for antibiotics, bone drugs, water pills and acid reducers.
Blood thinners (warfarin)
- Coenzyme Q10Reported to reduce warfarin's effect; your INR may need checking. (Linus Pauling Institute, Coenzyme Q10)
Diabetes medicines
- Alpha lipoic acidMay lower blood sugar further; check your glucose more often. (Linus Pauling Institute, Lipoic Acid)
Antibiotics (tetracyclines, quinolones)
- MagnesiumBinds these antibiotics; take them at least 2 hours before or 4-6 hours after. (NIH ODS, Magnesium)
Osteoporosis drugs (bisphosphonates)
- MagnesiumCan reduce absorption; separate by at least 2 hours. (NIH ODS, Magnesium)
Water pills and acid reducers (PPIs)
- MagnesiumThese drugs change magnesium levels; your doctor may check them. (NIH ODS, Magnesium)
Seizure medicines
- L-carnitineValproic acid and some other seizure drugs lower carnitine levels; ask your neurologist. (NIH ODS, Carnitine)
Liver problems or many medicines
- TurmericRare liver injury, mostly with high-absorption curcumin; stop and call a doctor for dark urine or yellow skin. (NIH LiverTox, Turmeric)
A starting list for a talk with your pharmacist, not a full interaction check. Keep taking prescribed medicine; never stop or change a dose because of a supplement.
Who should avoid magnesium glycinate or ask first?
Anyone with kidney disease should ask a doctor first, and so should anyone on the medicines above. The Synaptril label also excludes people under 18 and pregnant or nursing mothers.
The capsule holds five other ingredients, so its cautions are wider than magnesium's alone. See Synaptril side effects for the full list. A supplement can interact with medicines even when it is natural (NCCIH, Using Dietary Supplements Wisely).
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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.
More: magnesium glycinate, supplements and medicines and how much magnesium per day.
FAQ01
Synaptril questions people ask
Can magnesium glycinate cause diarrhea?
Yes, at high supplemental doses diarrhea is among the most common effects of magnesium. One Synaptril capsule has 80 mg, well under the 350 mg limit, which makes it less likely.
Can you take magnesium glycinate with antibiotics?
Only with spacing. Take tetracycline or quinolone antibiotics at least 2 hours before or 4-6 hours after magnesium, and ask your pharmacist about your antibiotic.
Is magnesium glycinate safe for people with kidney disease?
Ask a doctor first. Kidney disease changes how the body handles minerals, and our sources advise care. Do not start a magnesium supplement without that advice.
Who wrote this02
Written and reviewed by
Pages built from the label, the sales page and linked NIH, FDA, CDC, FTC and peer-reviewed sources.
Last updated . Learn about our editorial standards and how we check reviews. This website is run by a U.S. retail partner of Synaptril, not by the manufacturer or the distributor. We make money when you buy through our order links.
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