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Overview: Threonine is an amino acid that is naturally found in many common foods. Your body can’t make threonine on its own, but most people get enough of it from their diets. Supplements containing threonine seem to be well tolerated. Although these supplements are used for various reasons, their benefits for any use are not well defined. Before taking threonine, make sure to tell your health care provider about any medicines you are taking or health conditions you have, including allergic conditions.

Uses

What is threonine used for?

Threonine supplements are used for various reasons, but their benefits are not well defined. Some common reasons that people use threonine include the following.

  • To improve overall health
  • To improve bone and joint health
  • To improve gut health

Note: The FDA has not reviewed threonine for safety and effectiveness. Learn more about dietary supplements here.

How does threonine work (mechanism of action)?

Threonine is an amino acid, which is a building block of protein. Your body can’t make threonine on its own, so you must get it from your diet. Many foods contain threonine, including meats, fish, eggs, soy, nuts, seeds, and dairy products.

Your body uses threonine to build proteins and make another amino acid called glycine[1] , which plays an important role in brain function. Your cells also use threonine to create energy. The cells in your intestine use threonine to produce the mucus that helps to keep your gut healthy.

Due to threonine’s many effects in the body, there is interest in taking threonine supplements to improve brain, gut, and joint health. But there is no good evidence that these supplements are beneficial. Most people get enough threonine from their diets.

How should I store threonine?

You should store threonine according to the product label. Most dietary supplements should be kept in a cool, dry location that is out of the reach of children and pets and not in direct sunlight.

Side Effects

What are the most common side effects of threonine?

Threonine seems to be well tolerated. Tell your health care provider if you have any side effects that bother you.

There may be side effects of threonine that are not listed here. Contact your health care provider if you think you are having a side effect of a supplement. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of threonine?

While less common, the most serious side effects of threonine are described below, along with what to do if they happen.

Severe Allergic Reactions. Threonine may cause allergic reactions, which can be serious. Stop taking threonine and get help right away if you have any of the following symptoms of a serious allergic reaction.

  • Breathing problems or wheezing
  • Racing heart
  • Fever or general ill feeling
  • Swollen lymph nodes
  • Swelling of the face, lips, mouth, tongue, or throat
  • Trouble swallowing or throat tightness
  • Itching or skin rash
  • Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
  • Nausea or vomiting
  • Dizziness, feeling lightheaded, or fainting
  • Stomach cramps
  • Joint pain

Warnings & Precautions

Who should not use threonine?

Allergies to Ingredients. People who are allergic to any of the following should not take threonine.

  • L-threonine
  • Threonine
  • Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific threonine products they stock.

What should I know about threonine before using it?

Threonine is a dietary supplement. It cannot be marketed to treat or cure a disease.

Read and follow the directions on the specific product you are taking, or take it as recommended by your health care provider.

Keep threonine out of the reach of children.

The FDA has not tested threonine products to confirm that they contain the ingredients stated on their labels. Some dietary supplements have been tested by third-party organizations to confirm that they contain the ingredients listed on their labels and do not contain any harmful chemicals. Learn more about how to choose a safe dietary supplement product here.

What should I tell my health care provider before using threonine?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. Also tell them if you have an upcoming surgery planned. Sharing this information will help your health care provider know if this or other supplements are right for you.

In particular, make sure that you discuss any of the following.

Pregnancy. It is not known if or how threonine could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant.

Breastfeeding. Threonine is a natural part of breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does threonine interact with foods or drinks?

There are no known interactions between threonine and foods or drinks.

It is unknown if drinking alcohol will affect threonine.

Does threonine interact with medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

The interactions between threonine and medicines are not fully understood. As with most dietary supplements, the research on drug interactions with threonine is incomplete. Always check with your health care provider before taking threonine with any medicines.

Overdose/Missed Dose

What should I do if I accidentally use too much threonine?

If you or someone else has used too much threonine, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

Read the product label closely and speak to a health care provider about how to take threonine safely. Do not take double or extra doses, even if you miss a dose.