When to Take Glycine: Optimal Timing
Glycine is the smallest and simplest amino acid, and while it is conditionally essential rather than strictly essential, its roles in the body are wide-ranging: collagen synthesis, neurotransmission, creatine production, and regulation of sleep quality. Timing the intake of glycine supplementation can make a meaningful difference in which of these effects you prioritise.
With or Without Food
Glycine is generally well tolerated with or without food. Unlike many supplements, it does not cause significant gastrointestinal upset on an empty stomach. For collagen synthesis purposes — for example, when co-supplementing with vitamin C for joint or skin health — some research suggests taking glycine around 30 to 60 minutes before exercise may be more effective, as collagen precursors appear to be incorporated into connective tissue during the post-exercise remodelling period (Shaw et al., 2017).
For sleep purposes, taking glycine with a small snack or dissolved in warm water is common and practical. Large amounts of food alongside glycine are unlikely to meaningfully impair absorption but may slow gastric emptying, which is relevant if you are timing the dose for bedtime use.
Time of Day and Training
Evening / Bedtime Use
The best-characterised timing for glycine is before sleep. A double-blind crossover study found that ingestion of glycine before bedtime improved subjective sleep quality and reduced daytime sleepiness (Inagawa et al., 2006). A follow-up study using polysomnography found that glycine taken before sleep shortened the time to reach slow-wave sleep in subjects with mild sleep complaints (Bannai et al., 2012). These effects are thought to occur through lowering of core body temperature via peripheral vasodilation, which promotes sleep onset.
Based on available evidence, taking glycine approximately 30 to 60 minutes before bed appears to be the most evidence-supported timing strategy.
Pre-Workout
For connective tissue health and collagen synthesis, a protocol studied by Shaw et al. (2017) used a gelatin and vitamin C supplement taken 60 minutes before exercise. Given that glycine is the primary amino acid in gelatin, this timing window is relevant for those using glycine to support tendons, ligaments, or joint health in the context of training.
General Daily Use
When the primary goal is meeting overall dietary glycine needs — which may be suboptimal on a low-collagen diet (such as those not consuming skin, cartilage, or bone broth regularly) — the timing matters less. Splitting into two doses (morning and evening) or taking once daily at a consistent time is both practical and effective.
Split vs Single Dose
For sleep purposes, a single evening dose is most consistent with the research protocols. For collagen synthesis, a single pre-exercise dose is studied. For general amino acid repletion, splitting doses has no established advantage over a single dose but may be preferred for tolerability if taking larger amounts. Most supplement studies use doses of around 3 g for sleep outcomes.
Interactions Affecting Timing
- With creatine: If supplementing both, timing together or separately makes no meaningful difference as glycine is used endogenously in creatine synthesis over time, not immediately.
- With vitamin C for collagen: Taking together (within the same meal or supplement) is the studied approach — the vitamin C enhances collagen synthesis in the presence of glycine.
- With alcohol: Alcohol may interfere with sleep quality; taking glycine for sleep alongside alcohol is less likely to be effective.
- With magnesium: Both glycine and magnesium have sleep-supportive effects through different mechanisms. Taking them together in the evening is common and rational.
Practical Schedule
| Goal | Recommended Timing |
|---|---|
| Sleep quality | 3 g, 30–60 min before bed |
| Collagen synthesis / joint health | With vitamin C, 60 min before exercise |
| General dietary repletion | Once or twice daily, any time |
Products available at maxfit.ee include MST L-Glycine vegan 1000mg 120caps, MST L-Glycine vegan 1000mg 60caps, and OstroVit Glycine 200g Naturaalne. Browse the glycine category for the full range.
References
Inagawa, K., Hiraoka, T., Kohda, T., Yamadera, W., & Takahashi, M. (2006). Subjective effects of glycine ingestion before the sleep period on sleep quality. Sleep and Biological Rhythms, 4(1), 75-77. https://doi.org/10.1111/j.1479-8425.2006.00193.x
Bannai, M., Kawai, N., Ono, K., Nakahara, K., & Murakami, N. (2012). The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers. Frontiers in Neurology, 3, 61. https://pubmed.ncbi.nlm.nih.gov/22529837/
Shaw, G., Lee-Barthel, A., Ross, M. L., Wang, B., & Baar, K. (2017). Vitamin C-enriched gelatin supplementation before intermittent activity augments collagen synthesis. American Journal of Clinical Nutrition, 105(1), 136-143. https://pubmed.ncbi.nlm.nih.gov/27852613/
FAQ
Can I take glycine in the morning instead of at night?
Yes, especially if your goal is collagen synthesis, general amino acid intake, or creatine support. However, for sleep benefits specifically, the evidence points to evening or bedtime use. Morning glycine is not contraindicated — it simply is not the timing studied for sleep outcomes.
How much glycine should I take for sleep?
The studies showing sleep benefits used around 3 g before bed. This is well within the amounts found in supplement products. There is no established evidence that higher doses produce proportionally greater sleep benefits.
Does glycine interact with other sleep supplements?
Glycine and magnesium (including magnesium glycinate, which directly contains glycine) are commonly combined. Both are considered safe together. Adding melatonin to glycine has not been specifically studied in combination but there is no known interaction. Always check with a healthcare provider if combining multiple sleep-support supplements.
