L-Theanine side effects
Across 3,475 first-hand reports, people mentioned a side effect 156 times (about 4 per 100 reports). The most common: drowsiness, vivid dreams, fatigue. User reports show what people notice — they can't tell you whether L-Theanine is safe for you.
Reported side effects
drowsiness87
vivid dreams24
fatigue19
headache9
anhedonia8
tolerance6
sleep disruption2
low blood1
What got worse for some people
In their own words
“This stuff truly works... I'm really surprised how much this supplement has helped with the generalized anxiety.”
“Per weight I get more anxiety relief from theanine than I do phenibut.”
“I periodically take high doses of l-theanine and in no way does it feel like alcohol. It doesn't directly impact GABA-A/B receptors at all.”
“I practice good sleep hygiene, but thus far I've not seen any notable improvements that are repeatable.”
“Other sleep supplements failed at helping me (I've tried l-theanine, taurine, bacopa and ashwagandha)”
“Since starting (200mg twice a day) I’ve almost completely lost the urge to drink.”
Is L-Theanine safe? What the research covers
AResearch: Strong18 meta-analyses · 78 randomized trials on PubMed
None of the top reviews we found focus on safety. All research on L-Theanine.