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Caffeine + L-Theanine - Increased focus and concentration
Caffeine + L-Theanine - Increased focus and concentration - Supplement Facts
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Caffeine + L-theanine

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Combining caffeine and the relaxing amino acid L-theanine, found naturally in tea, produces synergistic effects which provide wakefulness that is calmed by the gentle effects of L-theanine.

Caffeine + L-Theanine Combination Benefits

  • May improve cognitive performance 
  • Promotes the benefits of caffeine without unwanted effects 
  • Supports focus and attention 
  • Promotes wakefulness and alertness 
  • L-Theanine is General Recognized As Safe (GRAS) by U.S. FDA

Product Description

Caffeine + L-Theanine Mode of Action


L-Theanine is an amino acid that naturally occurs in tea leaves and some forms of mushrooms.  Tea (Camellia sinensis) contains 1-3% of L-theanine. It is used in a supplemental form isolated directly from tea leaves or prepared via chemical synthesis or biosynthesis. Green, black, oolong and white tea all contain L-Theanine in varying amounts.

L-Theanine is absorbed through the intestines and reaches the blood-brain barrier in approximately 50 minutes after ingestion, similarly to the absorption through natural tea leaves.  L-Theanine can be found in the brain in the hippocampus after ingestion–the area of the brain responsible for learning and memory.

Research in animals suggests that L-Theanine (L-gamma-glutamyl-ethyl amide) works through glutamate receptors and increases levels of GABA and glycine in the brain, which causes relaxation. Increased GABA and glycine may increase serotonin and dopamine; however, it has also been noted that theanine may decrease or inhibit serotonin synthesis.


Caffeine is a stimulant found in coffee, tea, chocolate, guarana, yerba mate, and the kola nut.  It is an adenosine receptor antagonist, meaning that it prevents adenosine from being active.  Adenosine is one of the neurotransmitters responsible for drowsiness, and caffeine provides wakefulness through this mechanism of blocking adenosine.

Caffeine also interacts with the serotonergic system and can cause changes in the acetylcholine and dopamine systems within the body. Caffeine does produce side effects, such as large amounts of acutely raising blood pressure. Mild side effects can include anxiety, agitation, restlessness, fidgeting, irritability, elevated or irregular heart rate, and others. 

L-Theanine + Caffeine Combination

By combining L-theanine with caffeine, some of the undesirable side effects of caffeine use are lessened.  L-Theanine reduces caffeine’s stimulatory effects without modifying the other mechanisms for focus that caffeine offers.  L-Theanine interacts with caffeine by “taking the edge off” and still allows the alertness provided by caffeine to remain.

The combination of L-theanine with caffeine also may improve cognitive function, may eliminate the blood vessel constriction normally experienced with caffeine, and help keep the mind from experiencing wandering, or distraction.

The cognitive benefits associated with caffeine in combination with L-Theanine were studied on 50 mg caffeine to 100 mg L-Theanine, so we recommend caffeine to L-Theanine ratio should be 1-part caffeine to 2 parts L-Theanine.

Caffeine + L-Theanine Dosage

Pure Nootropics’ Caffeine + L-Theanine provides 100 mg of caffeine and 200 mg of L-Theanine per 1 capsule.  Suggested use for adults is 1 capsule by mouth once daily, or as directed by your healthcare practitioner.

Caffeine + L-Theanine Side Effects and Toxicity

  • L-Theanine Side Effects

L-Theanine, regardless of chemical synthesis, biosynthesis, or naturally occurring, is General Recognized As Safe (GRAS) by U.S. FDA.

L-Theanine is very well tolerated and side effects may include headaches and increased sleepiness. Animal research indicates that the No Observed Adverse Effect Level of L-theanine is greater than 4000 mg/kg in rats.

(Note:  Due to L-Theanine’s effects on reducing blood pressure, please see the list of possible interactions with pharmaceutical blood pressure medications)

Using Herbs and supplements that lower blood pressure should also be avoided when taking L-Theanine due to the same mechanism of L-Theanine on blood pressure that applies to pharmaceutical medications. Some of these herbs and supplements include casein peptides, cat’s claw, Andrographis, coenzyme Q10, L-arginine, fish oil, lyceum, stinging nettle, and others.

L-Theanine may reduce the effects of caffeine and mask the symptoms of taking too much caffeine.  These include the effects of energy drinks, coffee, black tea, oolong tea, guarana, mate, cola, and others.  Please be aware of your caffeine consumption during supplementation with L-Theanine.

  • Caffeine Side Effects

 In moderate doses, caffeine is usually well-tolerated in adults and children.  Side effects may include insomnia, restlessness, nervousness, nausea, vomiting, gastric irritation, tachycardia, tremors, quickened respiration, convulsions, headache, agitation, anxiety, chest pain, and irregular heartbeat.  Large doses of caffeine may cause tachycardia, metabolic acidosis, ketosis, and hyperglycemia.  Children and the elderly may experience more adverse effects from caffeine.  Chronic use of large amounts of caffeine may cause tolerance, psychological dependence, and abrupt stopping of caffeine use may cause physical withdrawal symptoms.

The lethal dose of caffeine in adults is approximately 10-14 grams per kilogram, but fatality has also occurred at lower doses.

Caffeine has many pharmaceutical medication and herb interactions.  If you are taking any medications, herbs, or supplements, please consult your healthcare practitioner before beginning supplementation with caffeine.  

If you are taking any medications, herbs, or supplements, please consult your healthcare practitioner before beginning supplementation with caffeine.