Magnesium glycinate side effects

At supplement doses, the side effect reported most consistently across the research is mild, dose-related gastrointestinal upset — loose stools, cramping or nausea. It resolves when you lower the dose or stop. Serious effects are uncommon in people with normal kidney function and mostly show up when kidney function is impaired.

The one side effect the research keeps coming back to: GI upset

A 2023 review searched for every intervention study published between 1997 and 2022 that tested a single-ingredient magnesium product and reported diarrhea as an outcome. Of ten studies found — spanning 128 to 1,200 mg a day — seven reported no significant difference in diarrhea between the magnesium group and the control group. One meta-analysis in that review did find minor gastrointestinal differences between placebo and 520 mg/day, though dropout rates weren't significantly different between groups. A search of the FDA's adverse event database, limited to single-ingredient magnesium products, turned up only 40 attributable gastrointestinal cases, and roughly a third of those mentioned diarrhea specifically.

The pattern across this literature: GI upset is the effect that shows up as the dose rises, it's the reason regulators set a 350 mg/day upper limit on supplemental magnesium, and it's mild and reversible rather than dangerous. A second meta-analysis in the same review found that 3 of 13 studies, spanning 120 to 973 mg/day, reported diarrhea severe enough that some participants withdrew — though which treatment arm those withdrawals came from wasn't specified in two of the three.

What the 2023 diarrhea review actually found, by source

Source	Dose range	Finding
7 of 10 identified studies	128-1,200 mg/day	No significant difference in diarrhea vs. control
1 meta-analysis	520 mg/day vs. placebo	Minor GI differences; no significant difference in study withdrawals
1 meta-analysis	120-973 mg/day	3 of 13 studies reported diarrhea-related withdrawal
FDA adverse event database	Single-ingredient Mg products	40 attributable GI cases total; ~1 in 3 mentioned diarrhea

What one glycinate-specific trial found

A 2024 randomized crossover trial gave 40 healthy adults magnesium oxide, magnesium citrate, magnesium bisglycinate and a microencapsulated comparator product, then measured blood magnesium at 1, 4 and 6 hours. Oxide and citrate produced a measurable rise in blood magnesium; bisglycinate did not, at any timepoint measured. The same trial reported that side effects often associated with magnesium supplements — increased intestinal motility and a sensation of gastric heaviness — were more common across the three standard forms tested (including bisglycinate) than with the microencapsulated comparator, without breaking that side-effect rate out by individual form. The trial was funded by the maker of the comparator product, which is worth weighing when reading its conclusions.

What we won't claim

Magnesium glycinate is often marketed as gentler on the stomach than other forms. We don't make that claim. No adequately powered head-to-head trial has directly compared glycinate against citrate or oxide for GI tolerance in healthy adults, and the one trial above that did test bisglycinate directly didn't find it standing out favorably on absorption. "Gentler" isn't a claim the current research supports for this form specifically, whatever the marketing around it says.

Where it gets more serious

Real magnesium toxicity (hypermagnesemia) is a different, rarer picture from GI upset, and it's concentrated in people whose kidneys can't clear excess magnesium normally. An observational study of 746 adults with chronic kidney disease found that higher blood magnesium was associated with a greater risk of cardiovascular events and death, which is why doctors advise caution with magnesium supplements specifically in kidney disease. If you have kidney disease, ask your doctor before taking any magnesium supplement, regardless of the dose on the label.

Our label, for reference

Electric Tiger Magnesium Glycinate provides 275 mg of elemental magnesium per three-capsule serving — under the 350 mg/day supplemental upper limit the diarrhea data above is built around. Other ingredients: hypromellose (capsule), magnesium stearate, silicon dioxide, rice flour.

Questions people ask

What are the side effects of magnesium glycinate?

The most commonly reported effect at supplement doses is mild GI upset — loose stools, cramping or nausea — and it's dose-related. Serious side effects are uncommon in people with normal kidney function.

What is the downside of magnesium glycinate?

Beyond the possibility of GI upset at higher doses, the main practical downside is that no adequately powered trial has established magnesium glycinate as better absorbed or gentler than other forms, despite that being a common marketing claim for it.

Are there any side effects to magnesium glycinate specifically, versus other forms?

The one relevant head-to-head trial found bisglycinate produced no significant blood magnesium rise at any timepoint, while oxide and citrate did, and it was funded by a competing manufacturer. That's a reason for caution reading it, not a reason to ignore it.

How long do the effects of magnesium glycinate last?

See how long does magnesium glycinate take to work for what absorption and status-repletion trials actually measured on a timeline.

Can magnesium glycinate cause diarrhea?

Does magnesium glycinate cause diarrhea or constipation? covers this specific question in depth, including the dose-response data above.