Medical disclaimer: SnoozeVerdict summarizes what people say about sleep supplements on Reddit. It is not medical advice, and nothing here is meant to diagnose, treat, cure, or prevent any disease. These statements have not been evaluated by the Food and Drug Administration. Talk to your doctor or pharmacist before starting a supplement, especially if you are pregnant, take medicines (including sleep or mood medicines), or have a medical condition. Poor sleep that lasts for months, loud snoring or gasping at night, or falling asleep during the day while driving or working needs a doctor, not a supplement. Full disclaimer.

Magnesium · side effects reported by users

Magnesium glycinate Side Effects: What Reddit Users Report

107 of 1039 Reddit owner comments about Magnesium glycinate (10%) describe an unwanted effect. The effects people mention most are grogginess, drowsiness or fatigue, trouble sleeping or feeling wired and vivid dreams or nightmares. These are self-reports from Reddit sleep, insomnia and supplement communities (May 2026 to October 2026), not a measured side-effect rate, and many people report no problems at all.

Magnesium glycinate overall: 4.0 · tolerability 4.4 (higher means fewer unwanted-effect reports).

What people describe

Effect mentioned	Owner comments
Grogginess, drowsiness or fatigue	23
Trouble sleeping or feeling wired	17
Vivid dreams or nightmares	11
Headaches	7
Stomach upset or digestive changes	6
Racing heart or palpitations	3

How we counted: among the 107 comments that describe an unwanted effect, a category counts when a sentence names the effect with wording like "gave me" or "made me". Questions and sentences about an effect going away are skipped. One comment can count in more than one row, and keyword counts can include some unrelated mentions, so read the quotes below for context.

Most common complaints

Side effects: 90 owner comments
Morning grogginess: 19 owner comments
Taste & form: 10 owner comments

Safety notes from NIH and published research

The NIH upper limit for magnesium from supplements is 350 mg a day for adults unless a doctor advises more; higher doses commonly cause diarrhea, and people with kidney disease are at higher risk of magnesium build-up.^{[NIH Office of Dietary Supplements]}
Magnesium can reduce absorption of some antibiotics and osteoporosis drugs, so doses are usually spaced apart.^{[NIH Office of Dietary Supplements]}

Stop and talk to a doctor if an effect is severe or does not settle. Ask a pharmacist about interactions with any medicine you take.

In their words

3/5 Side effects
“magnesium glycinate gave me the worst insomnia, everyone says it helps sleep but my brain just would not shut off for hours”

owner comment via r/Supplements · 2026-09-08 · 153 upvotes

3/5 Morning grogginessSide effects
“magnesium glycinate knocks me out cold but i wake up groggy if i take too much”

owner comment via r/Supplements · 2026-08-07 · 38 upvotes

2/5 Side effects
“Glycinate absolutely ruins my sleep, I wake up gasping for air, and am constantly tossing and turning.”

owner comment via r/Supplements · 2026-10-09 · 38 upvotes

4/5 Side effectsFalling asleep faster
“Magnesium Glycinate. Everyone was screaming how great it was. It made me sleepy and feel drugged.”

owner comment via r/Supplements · 2026-05-11 · 23 upvotes

4/5 Morning grogginessSide effects
“For example, magnesium bisglycinate works wonders for my girlfriend's anxiety, whereas when I have it (and I've tried multiple times) I get an immense grogginess and depression the next day.”

owner comment via r/Supplements · 2026-06-05 · 12 upvotes

2/5 MoodSide effects
“I also have ADHD and also can't tolerate magnesium glycinate.”

owner comment via r/Supplements · 2026-09-08 · 8 upvotes

5/5 Stomach upsetSide effects
“I have to take it with food so it doesn't upset my stomach, but other than magnesium glycinate, it has been the most life changing supplement that I've found.”

owner comment via r/Supplements · 2026-09-01 · 2 upvotes

1/5 Side effects
“Just fyi some people have a paradoxical effect, including my self from magnesium glycinate and L- theanie.”

owner comment via r/insomnia · 2026-09-01 · 5 upvotes

Frequently asked

What side effects do people report with Magnesium glycinate?

107 of 1039 Reddit owner comments about Magnesium glycinate (10%) describe an unwanted effect; the ones mentioned most were grogginess, drowsiness or fatigue, trouble sleeping or feeling wired and vivid dreams or nightmares. These are self-reports, not a measured side-effect rate.

Is Magnesium glycinate safe?

Safety depends on your health and medicines. The NIH and other sources listed on this page note specific cautions. Ask a doctor or pharmacist before starting, especially if you take other medicines or are pregnant.

More on Magnesium glycinate

Compare side-effect reports: Melatonin vs Magnesium glycinate · Magnesium glycinate vs Magnesium L-threonate (Magtein) · Magnesium glycinate vs Magnesium taurate · Magnesium glycinate vs Glycine · L-theanine vs Magnesium glycinate · Apigenin vs Magnesium glycinate · Tart cherry vs Magnesium glycinate