Theanine for Fibromyalgia & Chronic Fatigue Syndrome

Theanine is an antioxidant that's found naturally in tea leaves and has a unique amino acid found to have positive qualities for relaxing and sleep quality. So far, it hasn't been studied specifically for fibromyalgia and chronic fatigue syndrome, but we do have studies suggesting that it may be effective in treating many symptoms of these conditions.

Research shows theanine may:

Those are a lot of benefits from a single substance, and especially from one that appears to be quite safe.

Tea steeps in a glass mug.
Jasmin Awad / EyeEm / Getty Images

Typical Dosage

Theanine is available in supplement form, frequently under the name l-theanine or under the brand name suntheanine. Some formulations may have other ingredients as well, so be sure to check the label so you know exactly what you're taking.

Because it hasn't been studied for these conditions, we don't have standard dosage recommendations for treating fibromyalgia or chronic fatigue syndrome. However, reports show that taking between 400-900 mg of L-theanine for up to eight weeks improves sleep quality. For other conditions, the typical recommended dosage is 100 to 200 mg per day. Some studies, though, have used up to 600 mg per day.

Getting Theanine via Your Diet

If you prefer to get theanine through your diet rather than from supplements, there's the good news: Studies have shown that theanine does cross the blood-brain barrier. That's not the case with a lot of things, including substances that your brain needs.

To get a therapeutic effect, it's believed that you need to have dietary levels of at least 50 mg per day. It may take more for you to notice an effect. Depending on the quality and strength of the tea, that's about three cups a day.

To get more theanine through your diet, you can drink black, green or white tea. The decaffeination process does not appear to lower theanine levels significantly, so decaf teas are an option as well. (Theanine isn't in herbal teas, however.)

Tea is really the only place you can get it naturally. The only other place theanine has been found in nature is in the Bay Boletus mushroom, which is native to parts of Europe and North America, but it's not one you can expect to find in your local supermarket.

Side Effects 

So far, researchers don't know of any significant negative side effects or drug interactions associated with theanine. A short-term study on rats showed that repeated, extremely high doses cause few or no apparent harmful effects.

That's pretty amazing when you consider that even the safest, most common drugs and, yes, supplements generally come with the risk of a few negative effects. With theanine, though, the only problem seems to be that you could consume too much caffeine and stimulants may have a negative effect on some people with fibromyalgia and chronic fatigue syndrome. Remember, though, that decaffeinated tea does still contain theanine.

Theanine also doesn't have any known negative interactions with other treatments.

We don't have any data so far on whether theanine is safe during pregnancy or while breastfeeding. 

A Word From Verywell

As you consider supplements for medicinal purposes, consider which ones are the best match for your symptoms and include your healthcare provider

and pharmacist in the decision-making process. Take a slow, cautious approach to starting any new treatment, including supplements. Also, consider a symptom journal to help you spot any changes, for the better or worse, that may follow a change in your treatment regimen.

1 Source
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Baba Y, Inagaki S, Nakagawa S, Kaneko T, Kobayashi M, Takihara T. Effects of l -theanine on cognitive function in middle-aged and older subjects: a randomized placebo-controlled study. Journal of Medicinal Food. 2021;24(4):333-341. doi.  10.1089/jmf.2020.4803.

Additional Reading

By Adrienne Dellwo
Adrienne Dellwo is an experienced journalist who was diagnosed with fibromyalgia and has written extensively on the topic.