Can Glycine Cause Insomnia? Side Effects Explained
August 11, 2026 · Arun Menon
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Glycine is very unlikely to cause insomnia. In sleep trials it did the opposite, helping people fall asleep faster and reach deep sleep sooner, and it was well tolerated. The main side effects reported are mild and occasional, such as light stomach upset or a soft stool at higher intakes. There is no good evidence that glycine keeps healthy people awake. If glycine seems to disrupt your sleep, the more likely culprit is something else in your routine or another ingredient in a blend. As with any supplement, people on certain medications should check with a doctor first.
It is a fair question to ask of anything you take for sleep: could it backfire? For glycine the honest answer is that the evidence points the other way, but a good article tells you the caveats too. Here they are.
Can glycine cause insomnia?
No, glycine is not known to cause insomnia. In controlled trials it shortened the time to fall asleep and to reach deep sleep, the opposite of insomnia. In Yamadera and colleagues (2007), 3g of glycine before bed improved sleep onset and deep-sleep latency in people with unsatisfactory sleep. There is no established mechanism by which glycine would keep a healthy person awake, and no trial reporting it as a cause of insomnia.
What are the side effects of glycine?
Glycine is generally well tolerated. The occasional side effects reported are mild, mainly light stomach upset, nausea or a soft stool, usually at higher intakes. It is an amino acid the body already uses, which is part of why it is well tolerated at the doses used for sleep. Most people notice nothing beyond feeling calmer before bed. If you get mild digestive discomfort, taking it with a little water or slightly earlier can help.
| Concern | What the evidence shows |
|---|---|
| Causes insomnia | No; trials show faster sleep onset, not less sleep |
| Common side effects | Mild and occasional: light stomach upset, soft stool |
| Tolerability at 3g | Well tolerated in the sleep studies |
| Daytime grogginess | Not typical; glycine is not a sedative hangover type |
Can too much glycine keep you awake?
There is no evidence that higher glycine doses cause wakefulness; the main downside of overdoing it is mild digestive upset, not insomnia. More glycine does not add sleep benefit, so there is no reason to exceed the studied 3g. If a very high intake bothers your stomach, that discomfort could disturb sleep indirectly, but that is a gut issue, not glycine keeping your brain switched on. See how much glycine you actually need.
Does glycine interact with medications?
Glycine can interact with a few specific medications, most notably the antipsychotic clozapine, so anyone on prescription medication should check with a doctor before supplementing. Glycine may reduce the effectiveness of clozapine. This is uncommon but important, and it is the main reason to run any new supplement past your prescriber if you take medication. When in doubt, ask.
Who should be cautious with glycine?
People on prescription medication, and anyone pregnant, nursing or managing a medical condition, should speak to a healthcare professional before taking glycine. For most healthy adults, glycine at the studied dose is well tolerated and unlikely to disturb sleep. If your sleep worsened after starting a sleep blend, look at the whole formula and your routine, not just the glycine. See the complete guide to glycine for sleep.
Glycine at a studied, well-tolerated dose
REINCARN Night Reboot is melatonin-free, with Maizinol UP165 250mg, Glycine 3000mg, Magnesium Bisglycinate 300mg, L-Theanine 200mg, KSM-66 Ashwagandha 300mg, Tagara Root 300mg and Vitamin B6, for a disclosed 4,352mg total across 7 ingredients. For adults 18 and over.
See the formulaFrequently asked questions
Can glycine cause insomnia?
No. Glycine is not known to cause insomnia. In trials it shortened the time to fall asleep and to reach deep sleep, and was well tolerated. There is no mechanism by which it would keep a healthy person awake.
What are glycine's side effects?
They are mild and occasional, mainly light stomach upset, nausea or a soft stool, usually at higher intakes. Most people notice nothing beyond feeling calmer before bed.
Can too much glycine keep me awake?
There is no evidence higher doses cause wakefulness. The main downside of overdoing it is mild digestive upset, and there is no benefit to exceeding the studied 3g dose.
Does glycine interact with any medications?
It can interact with a few, most notably the antipsychotic clozapine, whose effect glycine may reduce. Anyone on prescription medication should check with a doctor before supplementing.
The bottom line. Glycine causing insomnia is a worry the evidence simply does not support, it helps sleep rather than blocks it, and its side effects are mild and rare. The real caution is medication interactions, which is a reason to ask your doctor, not to fear the amino acid. So if a sleep blend seemed to backfire, is glycine really the suspect, or is something else in the mix?
We translate primary sleep research into practical guidance for people who lead and perform.
References
- Thomas C, Kingshott RN, Allott KM, et al. Collagen peptide supplementation before bedtime reduces sleep fragmentation and improves cognitive function in physically active males with sleep complaints. Eur J Nutr. 2024;63(1):323-335. PMID 37874350.
- Yamadera W, Inagawa K, Chiba S, et al. Glycine ingestion improves subjective sleep quality in human volunteers, correlating with polysomnographic changes. Sleep Biol Rhythms. 2007;5(2):126-131.
Not medical advice. For informational purposes only. Consult a qualified healthcare professional before starting any supplement, especially if you are pregnant, nursing, take medication, or have a medical condition. REINCARN Night Reboot contains KSM-66 Ashwagandha and Tagara, which are not recommended in pregnancy or breastfeeding. For adults 18 and over.
Publisher disclosure. Published by REINCARN (Zandra Life Sciences Pvt. Ltd.). Regulated as a food supplement by the FSSAI. Corrections: reincarn@zandralifesciences.com.