Quick answer
Small trials report few side effects from GABA. At 300 mg a night for four weeks, 3 of 30 people reported mild stomach discomfort, headache or drowsiness. Far larger amounts, 6 g a day for a week, brought more minor complaints such as sore throat and dizziness, but nothing serious.1,2
Key facts
- In the four-week sleep trial, 1 of 10 people on placebo also reported a side effect.1
- Large single doses changed hormone levels, including growth hormone, in short studies.2,3
- The longest daily trials we found ran about three months.4,5
- FDA has not finished evaluating GABA as a food ingredient.6
Side effects reported in trials
In a four-week trial of 300 mg a night, 3 of 30 people on GABA reported mild stomach discomfort, headache or drowsiness, against 1 of 10 on placebo, who reported drowsiness. None of these effects was severe.1
At 2 g three times a day for a week, minor complaints became more common: sore throat, a burning feeling in the throat or on the skin, headache and dizziness. None was serious.2
Both studies were small, with 40 and 12 people. Small studies can miss rare problems, so finding nothing serious is reassuring but is not a guarantee.1,2
Blood pressure and hormones
Large doses change hormone levels. A 2 g dose raised insulin, and glucagon when fasting, in healthy volunteers without changing blood sugar, and a 3 g dose raised growth hormone about fourfold.2,3
Some studies found GABA can lower blood pressure. In 39 adults with mild high blood pressure, a fermented milk containing GABA lowered systolic pressure by about 17 mmHg over 12 weeks, more than placebo. A 95-day trial of 1.5 g a day in adults aged 50 to 70 found no significant change.5,7
These changes matter most if you take a medicine that acts on the same thing. A drop in blood pressure could add to the effect of blood pressure medicine, and a rise in insulin could matter if you take medicine for diabetes. No official source documents an interaction, but these are good reasons to ask your doctor first.2,7
Is GABA safe long term?
In 26 women on a 90-day exercise program, 200 mg of GABA a day made no difference compared with placebo to body composition, measured blood markers or growth hormone.4
The longest studies we found lasted about three months. One gave 200 mg a day for 90 days to women on an exercise program and reported no adverse effects on the measures taken. The other gave 1.5 g a day for 95 days to adults aged 50 to 70, and its summary does not describe side effects. No study covers years of daily use.4,5
FDA has not finished evaluating GABA as a food ingredient: the one notice asking it to, filed by a GABA maker in 2015, was withdrawn before FDA reached a view.6
Who should ask first, including teens
- Teens and children: every study we found enrolled adults, so there is no evidence for people under 18. Ask a doctor first.8
- Pregnant or nursing: we found no study of GABA in pregnancy or breastfeeding.
- Anyone taking a sedative, a sleep medicine, or medicine for anxiety, seizures, blood pressure or diabetes.
Drug labels, MedlinePlus, LiverTox and NIH list no GABA interactions, which only means none has been documented. Show the bottle to your pharmacist if you take any prescription medicine.
Questions people ask
Is GABA safe to take every night?
Nightly use has been studied for up to four weeks for sleep, and daily use for about three months in other trials, with no serious problems reported. Longer use has not been studied.1,4
Can you become dependent on GABA?
Nobody knows yet. The authors of the largest sleep trial wrote that longer studies are needed to check for dependence and tolerance.1
Is GABA safe for teens?
It has not been studied in people under 18. The trials we found enrolled adults, so ask a doctor before a teen takes it.8
See what we make
Every product shows its whole label and what its lab report covers. The store opens soon.
Sources
- Byun JI, Shin YY, Chung SE, Shin WC. Safety and Efficacy of Gamma-Aminobutyric Acid from Fermented Rice Germ in Patients with Insomnia Symptoms: A Randomized, Double-Blind Trial. J Clin Neurol. 2018;14(3):291-295. Opened 2026-10-07.
- Li J, Zhang Z, Liu X, et al. Study of GABA in Healthy Volunteers: Pharmacokinetics and Pharmacodynamics. Front Pharmacol. 2015;6:260. Opened 2026-10-07.
- Powers ME, Yarrow JF, McCoy SC, Borst SE. Growth hormone isoform responses to GABA ingestion at rest and after exercise. Med Sci Sports Exerc. 2008;40(1):104-110. Opened 2026-10-07.
- de Medeiros Pires LV, de Barros Martins A, Trindade CMO, et al. Effects of combined gamma aminobutyric acid supplementation and exercise training on the body composition of women: A randomized double-blind trial. Clin Nutr ESPEN. 2025;68:81-87. Opened 2026-10-07.
- de Bie TH, Witkamp RF, Balvers MG, Jongsma MA. Effects of γ-aminobutyric acid supplementation on glucose control in adults with prediabetes: A double-blind, randomized, placebo-controlled trial. Am J Clin Nutr. 2023;118(3):708-719. Opened 2026-10-07.
- U.S. Food and Drug Administration. GRAS Notice Inventory, GRN No. 595: gamma-aminobutyric acid. Filed September 1, 2015; evaluation stopped November 10, 2015, at the notifier's request. Opened 2026-10-07.
- Inoue K, Shirai T, Ochiai H, Kasao M, Hayakawa K, Kimura M, Sansawa H. Blood-pressure-lowering effect of a novel fermented milk containing gamma-aminobutyric acid (GABA) in mild hypertensives. Eur J Clin Nutr. 2003;57(3):490-495. Opened 2026-10-07.
- Hepsomali P, Groeger JA, Nishihira J, Scholey A. Effects of Oral Gamma-Aminobutyric Acid (GABA) Administration on Stress and Sleep in Humans: A Systematic Review. Front Neurosci. 2020;14:923. Opened 2026-10-07.
This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.