Short answer: L-theanine is not banned by the NCAA, but a Division I school most likely cannot provide it, because amino acids are not one of the six supplement types schools may give out [1][2]. That second part is our reading of the rule, so confirm it with your compliance office. The same is true of glycine, the other amino acid sold for calm and sleep. The catch is what comes with theanine: it is a common energy drink ingredient next to caffeine [4], and caffeine is on the NCAA banned list as a stimulant [1]. A drug test only counts caffeine as positive above a set urine limit, as our caffeine guide explains.
L-theanine, glycine and the NCAA at a glance
| Question | Answer |
|---|---|
| Are L-theanine or glycine on the NCAA banned list? | No. Neither is in any of the eight banned drug classes [1] |
| Can a Division I school give athletes either one? | Probably not. Amino acids are not one of the six types schools may provide [2] |
| What is the main risk in a theanine product? | Caffeine or green tea extract in the same product. Both count as caffeine, a banned stimulant [1], though a test is only positive above a set urine limit |
| Do they help you sleep? | The evidence is limited for theanine and thin for glycine [3][7][9] |
| Is there an NCAA approved L-theanine or glycine? | No. The NCAA approves no supplements [1] |
What is L-theanine?
L-theanine is an amino acid found in tea leaves. Unlike the amino acids in protein powder, your body does not use it to build proteins [3]. A 2025 review reports that white, green, oolong and black teas contain 0.9 to 3.1 percent theanine by dry weight of the leaf [3]. Supplement theanine is also made synthetically and marketed for relaxation and focus [3].
Why can a theanine product cause a positive test?
Theanine is not the problem. Its neighbors can be:
- It is a common partner for caffeine. The International Society of Sports Nutrition (ISSN) lists L-theanine among the common ingredients of energy drinks. In the bestselling energy drinks and shots it reviewed, 17.3 percent contained L-theanine, and every product in the sample contained caffeine [4].
- The caffeine may be doing much of the work. A 2014 review found moderate gains in alertness and attention in the first two hours after caffeine and theanine taken together. The size of the effect tended to track the caffeine dose more than the theanine dose [5].
- Tea based ingredients bring caffeine. The NCAA lists caffeine and its sources, including green tea extract, guarana and yerba mate, as banned stimulants [1]. The National Center for Complementary and Integrative Health (NCCIH) notes that green tea contains caffeine, and that liver injury, though uncommon, has been reported mainly with green tea extract pills [6].
So a "theanine" product for calm or focus may also contain caffeine. Our guide to whether caffeine is banned by the NCAA explains the urine limit, and our pre workout guide covers stimulant blends.
Does L-theanine actually help you sleep?
Maybe a little. A 2025 review looked at 19 randomized trial reports with 897 people. It found small improvements in how quickly people felt they fell asleep, how well they functioned during the day, and how they rated their sleep overall [7]. But those were self reported, and the authors said there are not enough studies of pure L-theanine on its own [7].
Another 2025 review was more cautious. It said there are no gold standard trials of theanine for falling and staying asleep, noted that many studies used theanine from one commercial source, and concluded that the science does not yet match the hype [3].
What about glycine for sleep?
Glycine is a nonessential amino acid [8]. Its sleep claims rest on a small set of studies, some of them by scientists working in a private company's research labs [8][9].
That evidence is thin:
- Three tiny trials. A 2023 systematic review found three studies in adults where glycine before bed improved sleep quality, alertness or fatigue. They had 10 to 19 participants each and lasted two to four days [9].
- High risk of bias. The review said these studies had a high risk of bias and should be read with caution [9].
- Not athlete studies. The review describes the groups as healthy adults or adults unhappy with their sleep [9].
That is a reason to be skeptical, not proof that it does nothing.
Is there an NCAA approved L-theanine or glycine?
No. There are no NCAA approved supplements, any supplement may contain banned substances not on the label, and you take them at your own risk [1]. Third party tested products may be options, but no product removes the risk completely [1]. Our guides to NSF Certified for Sport, Informed Sport and BSCG Certified Drug Free explain what each program checks. Informed Sport, for example, tests every batch before release [11].
Can a Division I school provide L-theanine or glycine?
Probably not. NCAA rules (Bylaw 16.5.2.7) let a Division I school provide supplements "for the purpose of providing additional calories and electrolytes," in six types only: carbohydrate and electrolyte drinks, energy bars, carbohydrate boosters, protein supplements, omega 3 fatty acids, and vitamins and minerals [2].
Neither theanine nor glycine fits those types. That is our reading of the rule, not an NCAA ruling, and our BCAA guide explains why amino acids are a gray area. Your compliance office makes the call. For a label your staff are unsure about, your school can use Drug Free Sport AXIS, the only label review service the NCAA subscribes to [1].
Banned is about your drug test; impermissible is about what your school may hand out. Our creatine guide explains the difference.
What about high school athletes?
The NCAA does not govern high school sport. The NFHS position statement does not address L-theanine or glycine by name. It lists "protein powders and amino acids" as legal and not banned for competition, describes amino acids as products marketed for muscle building, and says athletes should discuss their use with a knowledgeable health care provider [10]. Your state association and school set the actual rules, so ask your athletic trainer.
Checklist before you use a theanine or glycine product
- Scan it in Varsity Stack first. Check the barcode or label against our certification database before you buy.
- Ask your athletics staff. The NCAA makes checking with them your responsibility [1].
- Look for hidden caffeine. Check for caffeine, green tea extract, guarana and yerba mate, which all count as caffeine, a banned stimulant [1].
- Read the whole blend. The NCAA list is not complete, and anything related to a banned class is also banned [1].
- Choose a certified product and match the batch on the certifier's own site.
For every banned class in one place, see our NCAA banned substances guide. For other sleep products, see whether melatonin or magnesium is banned by the NCAA. For collagen, see whether collagen is allowed in the NCAA.
Check a theanine or glycine product with Varsity Stack
The fastest way to check a theanine or glycine product is the free Varsity Stack app. Scan the barcode or snap a photo of the label, and Varsity Stack checks it against our certification database before you buy. Then log it with the rest of your stack, so you and your staff always know what you are taking.
For coaches, sports dietitians and athletic trainers: the team dashboard shows every athlete's stack, the certification status of each product and its full ingredient panel. Athletes scan what they buy, and staff approve or reject it for the roster, for example a focus product that also lists caffeine. Request access for your program.
Varsity Stack does not laboratory test supplements, and certification lowers risk without removing it.
Varsity Stack does not provide medical, legal or NCAA compliance advice. This article is for educational purposes only. Consult a qualified healthcare provider or registered dietitian before starting any supplement regimen. Check current NCAA legislation and Drug Free Sport AXIS with your compliance staff when reviewing individual products.
Sources
- NCAA, 2026 to 27 NCAA Banned Substances
- NCAA, 2026 to 27 NCAA Division I Manual, Bylaw 16.5.2.7 Nutritional Supplements
- Dashwood R and Visioli F, l-theanine: From tea leaf to trending supplement, does the science match the hype for brain health and relaxation?, Nutrition Research, 2025
- Jagim AR and colleagues, International Society of Sports Nutrition position stand: energy drinks and energy shots, Journal of the International Society of Sports Nutrition, 2023
- Camfield DA and colleagues, Acute effects of tea constituents L-theanine, caffeine, and epigallocatechin gallate on cognitive function and mood: a systematic review and meta-analysis, Nutrition Reviews, 2014
- NCCIH, Green Tea: Usefulness and Safety (February 2025)
- Bulman A and colleagues, The effects of L-theanine consumption on sleep outcomes: a systematic review and meta-analysis, Sleep Medicine Reviews, 2025
- Bannai M and Kawai N, New therapeutic strategy for amino acid medicine: glycine improves the quality of sleep, Journal of Pharmacological Sciences, 2012
- Soh J and colleagues, The effect of glycine administration on the characteristics of physiological systems in human adults: a systematic review, GeroScience, 2024
- NFHS Sports Medicine Advisory Committee, Position Statement on Appearance and Performance Enhancing Drugs and Substances (October 2024)
- Informed Sport, Athletes
