Overview

Glycine is an amino acid that your body uses to build proteins and regulate brain signals. Glycine supplements seem to be well tolerated. They are often taken for many reasons, but their benefits for any use are not well defined. Before taking glycine, tell your health care provider about all of your health conditions and any medicines or supplements you may be using, especially for seizures, dementia, or schizophrenia.

Uses

What is glycine used for?

Glycine is used for various reasons, but its benefits are not well defined. Some common reasons for using glycine include the following.

• Trouble sleeping (insomnia)
• To help with relaxation
• To improve brain health
• To improve physical performance

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

How does glycine work (mechanism of action)?

Glycine is an amino acid. It helps make many important substances in the body, including proteins, creatine, and hemoglobin. It also helps regulate the signals that are sent in your brain. Your body makes glycine from substances that are naturally found in your diet, such as serine, choline, and threonine. You can also get glycine directly from high-protein foods in your diet, including meat, beans, and tofu.

Glycine can act on many different brain receptors that help regulate and modify brain signals. One of these receptors, called N-methyl-D-aspartate (NMDA), plays an important role in dementia, schizophrenia, and some mood disorders. But research on taking glycine for brain health is very limited, and it is not clear if taking glycine can help with any of these conditions. NMDA receptors may also play a role in sleep, leading to interest in taking glycine to help with sleep problems and relaxation. But the benefits of glycine for these uses are not well defined.

Glycine may help reduce swelling (inflammation) in the body. Some people claim that taking glycine supplements may help reduce low-level inflammation throughout the body. Glycine supplements may also help with physical performance and recovery after exercise. But there is no clear evidence that glycine can help with any of these uses.

How should I store glycine?

You should store glycine 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 glycine?

Glycine 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 glycine 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 glycine?

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

Severe Allergic Reactions. Glycine may cause allergic reactions, which can be serious. Stop taking glycine 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

Precautions

Who should not use glycine?

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

• Aminoacetic acid
• Aminoethanoic acid
• Glycine
• Any of the ingredients in the specific product

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

What should I know about glycine before using it?

Glycine 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 glycine out of the reach of children.

Glycine is available in dietary supplements that may contain multiple other ingredients. Some products also contain glycine in other forms. For example, some supplements contain magnesium glycinate, which can increase the levels of both magnesium and glycine in your body. Read the product label carefully to see which ingredients it contains.

If you are taking glycine powder, use an appropriate measuring device to measure the powder, such as the device included with the product. Read the label carefully and measure the amount stated on the label.

The FDA has not tested glycine 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 glycine?

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. This will help them know if glycine is right for you.

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

Other Medicines and Supplements.Glycine may interact with other medicines and supplements. Before taking glycine, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

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

Breastfeeding. It is not known if glycine passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does glycine interact with foods or drinks?

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

It is unknown if drinking alcohol will affect glycine.

Does glycine 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.

In particular, make sure that you discuss if you are taking any of the following before taking glycine.

• Any medicine for seizures, such as carbamazepine, phenobarbital, or valproic acid
• Clozapine (Clozaril), which is a medicine for schizophrenia
• Memantine (Namenda), which is a medicine for dementia

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

Dosing

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

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

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