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L-Theanine and Caffeine: Can This Combo Improve Sleep?

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March 13, 2025

L-Theanine and Caffeine: Can This Combo Improve Sleep?

Medically reviewed by: 

Dr. Shiyan Ooi

School of Medical Sciences, University of Manchester

L-Theanine and caffeine are often taken together to enhance focus and reduce stress, but can this combination also benefit sleep quality? Understanding how these two compounds interact can help determine their effects on rest.

How L-Theanine and Caffeine Work Together

L-Theanine and caffeine have complementary effects:

  • L-Theanine: Promotes relaxation by increasing alpha brain waves and enhancing GABA production.
  • Caffeine: Increases alertness by blocking adenosine, a neurotransmitter responsible for drowsiness.

When taken together, L-Theanine helps smooth out the stimulating effects of caffeine, reducing jitteriness and improving focus (National Institutes of Health).

Does the Combo Affect Sleep?

While caffeine can disrupt sleep if consumed too late in the day, L-Theanine may help mitigate some of its negative effects by:

  • Reducing stress and promoting relaxation
  • Lowering heart rate and blood pressure
  • Enhancing overall sleep quality when taken separately from caffeine

Best Practices for Taking L-Theanine and Caffeine

To optimize cognitive benefits without harming sleep, consider:

  • Taking the combination in the morning or early afternoon
  • Using a 2:1 L-Theanine to caffeine ratio (e.g., 200 mg L-Theanine with 100 mg caffeine)
  • Avoiding caffeine at least 6 hours before bedtime

Conclusion

While L-Theanine and caffeine together enhance focus and relaxation, caffeine should be avoided too close to bedtime. L-Theanine alone may still offer sleep benefits when taken separately.

Dr. Shiyan Ooi

Dr. Shiyan Ooi is a medical doctor with over a decade of experience treating patients with chronic conditions. She graduated from the University of Manchester with a Bachelor of Medicine and Surgery (MBChB UK) and spent several years working at the National Health Service (NHS) in the United Kingdom, several Singapore government hospitals, and private functional medicine hospitals. Dr. Ooi specializes in root cause analysis, addressing hormonal, gut health, and lifestyle factors to treat chronic conditions. Drawing from her own experiences, she is dedicated to empowering others to optimize their health. She loves traveling, exploring nature, and spending quality time with family and friends.