If you have liver disease, kidney disease, or any other serious or chronic health condition, check with your healthcare provider before taking L-theanine. Safety of the supplement has not been determined at this time, so it is important to use caution while taking L-theanine products. Since very few L-theanine safety warnings and precautions are available, make sure to find a reputable manufacturer for your product.
L-theanine (also known as just theanine) is a dietary supplement used to treat a variety of conditions. You may not be able to take L-theanine safely 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:
- Pregnant or thinking of becoming pregnant
You should also be sure to tell your healthcare provider about all other medicines you are taking, including prescription and non-prescription medicines, vitamins, and herbal supplements.
Warnings and precautions to be aware of concerning the safety of L-theanine include the following:
- If you have liver or kidney disease, check with your healthcare provider before taking any medication or supplement, including L-theanine. Many medications and supplements are cleared from the body using the liver and kidneys.
- Check with your healthcare provider before taking L-theanine if you have any chronic or serious health conditions.
- L-theanine supplements can interact with some medications (see L-Theanine Drug Interactions for more information).
- If you decide to use supplements (such as L-theanine), what you see on the label may not reflect what is in the bottle. For example, some herbal supplements have been found to be contaminated with heavy metals or prescription drugs, and some have been found to have much more or much less of the featured ingredient than their label states. Therefore, make sure the manufacturer of your L-theanine product is a trusted and reputable manufacturer. It is a good sign if a manufacturer abides by the rules of Good Manufacturing Practices (GMP) for drugs. It is also a good sign if a product has the United States Pharmacopoeia (USP) seal, which means that the product has been independently tested and shown to contain the correct ingredients in the amounts listed on the label. Your pharmacist is a good resource for information about which manufacturers are most reputable.
- It is not known whether L-theanine is safe for pregnant or breastfeeding women (see L-Theanine and Pregnancy and L-Theanine and Breastfeeding).