Signal reading for
Sleep quality
A 2026 scoping review found only three trials of supplemental glycine and sleep [1]; the human trials we could trace were small crossover studies, with 7 to 19 participants, from researchers tied to a glycine manufacturer [2] [3].
Independent, larger randomized trials with objective sleep measures would move this reading.
What the research shows
- Only three glycine-and-sleep trials turned up in a 2026 scoping review; all reported a benefit on at least one sleep-related outcome [1].
- The trials we traced analyzed 19, 11 and 7 people, all used 3 g before bed, and all involved researchers affiliated with a glycine producer [2] [3].
- Proposed mechanisms, such as a small drop in core body temperature, come largely from rat studies [2] [4].
What the hype says
- Evening-routine content often presents glycine as an inexpensive powder to stir into water before bed.
- Social posts tend to group it with magnesium as part of a bedtime supplement stack.
- Wellness writing sometimes frames it as a way to feel sharper the next morning.
Hype is described in our words, not quoted, and is not a claim by this site.
The short version
- A single-ingredient powder: 3 g of free-form glycine per 3/4 level teaspoon, about 151 servings per 1 lb bottle, no other ingredients.
- $18.37 on Sep 30, 2026, or about $0.12 per 3 g serving.
- The research dose is 3 g before bed; the label suggests 1/4 to 3/4 teaspoon a day without naming a time.
What the label shows
We read the Supplement Facts panel and the suggested-use and caution panels from the bottle images on the Amazon listing for the 1 lb (454 g) size on Sep 30, 2026.
| Ingredient | Amount per serving | What to know |
|---|---|---|
| Glycine (free-form) | 3 g (3,000 mg) | Per 3/4 level teaspoon. No Daily Value exists for glycine. |
| Calories | 10 | Glycine is an amino acid, so it carries a few calories. |
| Other ingredients | None | A single-ingredient, unflavored powder. |
The bottle's suggested use is 1/4 to 3/4 level teaspoon daily in water or juice, preferably on an empty stomach; the listing's text version words the directions differently (1/4 teaspoon one to three times daily), so the bottle label is what we relied on. Its caution says the product is for adults only and to consult a physician if pregnant or nursing, taking medication, or managing a medical condition. The front-label lines about sleep and nervous-system support, and the listing title's cognitive line, are the seller's structure/function wording.
What the research shows
Scoping review. A 2026 scoping review in the Journal of Dietary Supplements searched four databases for clinical studies of glycine absorption and of glycine or collagen supplements on sleep [1]. It found 22 trials in all, but only three that tested supplemental glycine on sleep-related outcomes. All three reported a benefit on at least one outcome. The authors described glycine's role in sleep as biologically plausible and called for larger trials with standardized sleep measures.
The three trials. A 2012 review in the Journal of Pharmacological Sciences, written by researchers at a glycine manufacturer, describes the first two [2]. In the first, a randomized double-blind crossover trial published in 2006, 19 women with ongoing dissatisfaction with their sleep took 3 g of glycine or placebo before bed, and reported feeling less fatigued the next morning. In the second, a randomized single-blind crossover trial published in 2007, 11 adults with similar sleep complaints had their sleep recorded by polysomnography in a sleep lab; glycine was associated with shorter time to fall asleep and to reach deep sleep on the recordings, and with better self-rated sleep satisfaction. The third, a 2012 randomized single-blind crossover trial in Frontiers in Neurology, restricted sleep by 25% for three nights in healthy men [3]. Ten enrolled and seven were analyzed. With 3 g of glycine 30 minutes before bed, they rated themselves less fatigued the next day and did better on a reaction-time vigilance test. Three of its five authors worked for the same glycine producer, and the volunteers were that company's employees.
Animal work. In rats, oral glycine raised glycine levels in the blood and cerebrospinal fluid and lowered core body temperature, which the researchers link to the body's usual temperature dip at sleep onset [2]; a 2015 rat study traced those effects to receptors in the brain's body-clock region [4]. Mechanism studies in animals can explain why an effect might happen, but they do not show that it happens in people.
Where that leaves the reading. Three small crossover trials, from one research group with a commercial interest, measured over a few nights, is a thin file even though the results point the same way. That is a 2 on our scale, and it applies to sleep quality only.
Study dose vs. label dose
In the research
3 g before bed
Single evening doses over one to a few nights, in crossover trials [2] [3]
One serving of this product
3 g
Per 3/4 level teaspoon, per the label; suggested use 1/4 to 3/4 teaspoon daily
Where the hype comes from
Glycine is inexpensive and easy to take, which helps it travel in bedtime-routine content. The research story attached to it usually cites the same few Japanese studies, often without mentioning how small they were or that they came from a company that produces glycine. None of that means the findings are wrong, only that they have not been checked by independent groups at a larger scale.
The label limits this product to adults and asks anyone pregnant, nursing, taking medication or managing a medical condition to consult a physician first. The trials lasted only a few nights, so there is little controlled information on nightly use over months. Persistent trouble sleeping is worth raising with a clinician.
Price and where it is sold
On Sep 30, 2026 the Amazon listing for NOW Glycine powder, 1 lb, showed $18.37, in stock, sold by Amazon.com. The listing marked the item as non-returnable for food safety reasons. Check the listing for the price on the day you look.
Who should look elsewhere
- Anyone pregnant, nursing, taking medication or managing a medical condition, per the label's own caution, should check with a clinician first.
- People who want a measured scoop may find teaspoon measuring less precise; a small kitchen scale gives a steadier 3 g.
- Anyone who expects a well-established sleep aid should know the evidence here is limited to three small trials.
Sources
- Journal of Dietary Supplements. Scoping review of glycine bioavailability and sleep-related outcomes after glycine and collagen supplementation. 2026;23(5):602–622. PubMed
- Journal of Pharmacological Sciences. Review by glycine-manufacturer researchers of human trials (19 and 11 participants, 3 g before bed) and rat studies on glycine and sleep. 2012;118(2):145–148. PubMed
- Frontiers in Neurology. Randomized single-blind crossover trial of 3 g glycine at bedtime during three nights of partial sleep restriction in healthy men. 2012;3:61. PubMed
- Neuropsychopharmacology. Rat study on the brain receptors involved in glycine's effects on sleep and body temperature. 2015;40:1405–1416. PubMed
This entry is educational and is not medical advice. The signal reading describes published research on one use; it is not a recommendation to take anything. Ask a qualified clinician or pharmacist before starting any supplement, especially if you are pregnant, nursing, have an existing condition, or take medication.