NutriStack
L-Theanine and Metoprolol, a caution.
L-Theanine blunts stress-induced rises in blood pressure and heart rate in high-stress-responder subjects. Combined with metoprolol, the effect is usually mild but can deepen the drug's anxiolytic and cardiovascular effects, particularly when taken at the same time as a dose.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
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From the interaction database
What the row says.
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At a glance
- Substances
- L-Theanine and Metoprolol
- Pair type
- Caution
- Evidence (highest tier)
- Emerging
- Source citations
- 2 sources
- Stack Score effect
- −5 to your Stack Score (per scored caution row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Caution · Emerging evidence
Caution
What is happening. L-Theanine blunts stress-induced rises in blood pressure and heart rate in high-stress-responder subjects. Combined with metoprolol, the effect is usually mild but can deepen the drug's anxiolytic and cardiovascular effects, particularly when taken at the same time as a dose.
Mechanism. L-Theanine modulates GABA, glutamate, and catecholamine signaling, reducing sympathetic drive. This adds to metoprolol's beta1 antagonism, attenuating both basal and stress-evoked blood pressure and heart rate.
Recommendation. L-Theanine at typical doses (100-400 mg) is generally compatible with metoprolol. Monitor for additive sedation or lower-than-expected heart-rate readings, and reduce the dose if symptomatic.
Sources (2)
- Yoto A, Motoki M, Murao S, Yokogoshi H. Effects of L-theanine or caffeine intake on changes in blood pressure under physical and psychological stresses. J Physiol Anthropol. 2012;31(1):28. PMID 23107346
- Rogers PJ, Smith JE, Heatherley SV, Pleydell-Pearce CW. Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together. Psychopharmacology (Berl). 2008;195(4):569-77. PMID 17891480
Stack Score
How this pair moves the number.
Effect on the composite score
If both L-Theanine and Metoprolol are in the same stack, this pair applies −5 to your Stack Score (per scored caution row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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