Glycine Side Effects: What Reddit Users Report
20 of 281 Reddit owner comments about Glycine (7%) describe an unwanted effect. The effects people mention most are vivid dreams or nightmares and trouble sleeping or feeling wired. 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.
Glycine overall: 3.9 · tolerability 4.5 (higher means fewer unwanted-effect reports).
What people describe
| Effect mentioned | Owner comments |
|---|---|
| Vivid dreams or nightmares | 3 |
| Trouble sleeping or feeling wired | 3 |
How we counted: among the 20 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: 15 owner comments
- Falling asleep faster: 2 owner comments
- Taste & form: 2 owner comments
Safety notes from NIH and published research
- Supplements can interact with medicines and are not reviewed by the FDA for safety before they are sold; tell your doctor or pharmacist about anything you take.[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
2/5 Side effects“i experience a paradoxical effect to glycine, it gives me extreme anxiety & insomnia.”
2/5 Emotional bluntingMood“I'd like to add a caveat about glycine; it caused depression and anhedonia when I used it to support my sleep.”
1/5 Side effects“It turned out to be bad for me - I guess many can't tolerate the glycine.”
4/5 Side effectsDeeper sleep“I think certain people can't tolerate the Glycine.”
4/5 CalmingMorning grogginess“Its supposed to convert to L-glycine to some degree which is also supposed to promote sleep.”
1/5 Side effects“Glycine makes me feel absolutely awful \~ waking for multiple hours in the middle of the night, followed by anxiety the following day.”
2/5 Side effects“Magnesium glycinate didn't work for me because of the glycine - it kept me awake.”
3/5 Morning grogginessSide effects“The thing I've noticed is if I take mag glycine during the day, I do sleep better at night.”
Frequently asked
What side effects do people report with Glycine?
20 of 281 Reddit owner comments about Glycine (7%) describe an unwanted effect; the ones mentioned most were vivid dreams or nightmares and trouble sleeping or feeling wired. These are self-reports, not a measured side-effect rate.
Is Glycine 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 Glycine
Compare side-effect reports: Magnesium glycinate vs Glycine · L-theanine vs Glycine · Melatonin vs Glycine · Taurine vs Glycine