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Should You Take L-Theanine With Caffeine?
In one trial, L-theanine with caffeine improved some attention and memory measures and alertness compared with placebo.[1]
Based on Haskell et al., Biological Psychology 2008 · Updated October 10, 2026
L-theanine with caffeine improved attention in one trial[1]
In a crossover trial of 250 mg theanine with 150 mg caffeine, the combination improved some attention and memory measures and alertness compared with placebo.
This is one trial; it tested L-theanine and caffeine alone and together, each against placebo.
Source [1]Haskell CF, et al. The effects of L-theanine, caffeine and their combination on cognition and mood. Biological Psychology. 2008. (PubMed)
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Sources
- Haskell CF, et al. The effects of L-theanine, caffeine and their combination on cognition and mood. Biological Psychology. 2008. PubMed
This page is general information from the cited sources, not medical advice. If you take prescription medication, are pregnant, or manage a health condition, check supplement changes with a pharmacist or doctor.