L-Theanine

L-theanine is an amino acid found in tea and also used in dietary supplements. It is often claimed to be beneficial for treating Alzheimer's disease, high blood pressure, and anxiety. L-theanine may increase serotonin and GABA levels, lower norepinephrine levels, and protect brain nerves from damage seen in Alzheimer's. However, there is currently not enough evidence to confirm the effectiveness of L-theanine for any uses.

 

What Is L-Theanine?

L-theanine (also known as just theanine) is an amino acid found in tea. It is also used in dietary supplements and is claimed to be useful for a variety of different conditions such as anxiety, Alzheimer's disease, and high blood pressure (hypertension).
 
(Click Benefits of L-Theanine for more information on what L-theanine is used for, including additional L-theanine uses.)
 

How Does L-Theanine Work?

It is not exactly clear how L-theanine works. It might work for anxiety by increasing levels of gamma-aminobutyric acid (GABA), a brain chemical that is naturally calming. L-theanine may also increase serotonin levels in the brain. It is thought that L-theanine may also protect nerves in the brain from damage seen with Alzheimer's disease. In animals, L-theanine lowers norepinephrine levels, which may help lower blood pressure.
 

Is L-Theanine Effective?

There is not yet enough scientific evidence to evaluate the effectiveness of L-theanine for any use.
 
(Click Does L-Theanine Work? for more information.)
 

L-Theanine Dosing Information

A safe and effective L-theanine dose has not been established. Be sure to follow the specific instructions on your particular L-theanine product.
 
(Click L-Theanine Dosage for more information.)
 

Side Effects of L-Theanine

There are no known side effects of L-theanine. However, this probably reflects a lack of clinical studies with L-theanine (not a real absence of side effects).
 
(Click L-Theanine Side Effects to learn more, including what to do if you develop a potentially serious side effect.)
 

Drug Interactions With L-Theanine

L-theanine can interact with a few medications (see L-Theanine Drug Interactions).
 

Is L-Theanine Safe?

Some people may be more likely to experience problems due to L-theanine. Therefore, you should talk with your healthcare provider before taking L-theanine if you have:
 
  • Kidney disease, such as kidney failure (renal failure)
  • Liver disease, such as liver failure, cirrhosis, or hepatitis
  • Any other serious or chronic health condition
  • Any allergies, including allergies to food, dyes, or preservatives.
     
Also, let your healthcare provider know if you are:
 
Make sure to tell your healthcare provider about all other medicines you are taking, including prescription and non-prescription medicines, vitamins, and herbal supplements.
 
(Click L-Theanine Safety for more information, including any available L-Theanine warnings and precautions.)
 

What If I Take an L-Theanine Overdose?

It is not known exactly what to expect from an L-theanine overdose. If you think you may have taken too much L-theanine, seek medical attention immediately.
 
(Click L-Theanine Overdose for more information.)
 

L-Theanine: Storage Methods

Refer to the label of your individual L-theanine product for information on how to best store L-theanine. Keep L-theanine and all other medications or supplements out of the reach of children.
 
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Written by/reviewed by: Kristi Monson, PharmD; Arthur Schoenstadt, MD
Last reviewed by: Kristi Monson, PharmD;