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Overview: Ornithine is an amino acid that is naturally produced in the body and found in small amounts in various foods. It is available as an over-the-counter dietary supplement in capsule, tablet, and powder forms that are taken by mouth. People take ornithine for various reasons, such as stress relief, improving sleep, and athletic performance, although its benefits are not well defined. Ornithine seems to be well tolerated. The most commonly reported side effects are stomach issues, such as nausea, vomiting, or diarrhea. Check with your health care provider before using ornithine, especially if you have any health conditions or take any medicines.

Uses

What is ornithine used for?

Ornithine is used for various reasons, although its benefits are not well defined. Some common reasons people may take ornithine include the following.

A product called l-ornithine-l-aspartate (LOLA) is used in some countries for people with a liver condition called hepatic encephalopathy, which involves confusion and other brain symptoms caused by liver disease. LOLA is not the same as ornithine dietary supplements.

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

How does ornithine work (mechanism of action)?

Ornithine is a nonessential amino acid. This means the body can make it on its own. It is also found in small amounts in certain foods and beverages, such as fish, shellfish, and green tea. Ornithine is not used to build proteins but plays an important role in several processes in the body.

Ornithine is a key part of a natural process in the liver, called the urea cycle, that helps remove ammonia from the blood. Ammonia is a waste product that is made when the body breaks down protein.

Ornithine helps convert ammonia into urea, which is then removed from the body through urine. The body also uses ornithine to make other important natural substances, including proline (a building block of collagen, which is found in skin, bones, and connective tissue) and polyamines (substances involved in cell growth and repair).

However, the benefits of taking ornithine supplements for any use are not well defined.

Some research suggests that ornithine may stimulate the release of growth hormone through a pathway involving ghrelin, a hormone that plays a role in appetite and growth. But human studies have not consistently shown benefits for increased muscle mass, strength, or athletic performance.

Ornithine may also help lower stress or improve sleep by affecting cortisol, a stress hormone, although the research on this effect is limited.

How should I store ornithine?

You should store ornithine 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 ornithine?

The most common side effects of ornithine are listed below. These side effects may vary depending on the specific product or the dose you are taking. Tell your health care provider if you have any of these side effects that bother you.

  • Nausea
  • Vomiting
  • Stomach pain
  • Diarrhea

There may be other side effects of ornithine 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 ornithine?

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

Severe Allergic Reactions. Ornithine may cause allergic reactions, which can be serious. Stop taking ornithine 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 ornithine?

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

  • L-ornithine
  • Ornithine
  • Any of the ingredients in the specific product

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

Gyrate Atrophy or High Ornithine Levels. People with gyrate atrophy (a rare inherited eye disease that causes vision loss over time) should not take ornithine supplements unless their health care provider specifically recommends it. In people with gyrate atrophy, ornithine can build up in the blood and eye fluids. High ornithine levels may be harmful to the light-sensitive tissue at the back of the eye (retina) and may worsen vision problems.

What should I know about ornithine before using it?

Ornithine 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 ornithine out of the reach of children.

Ornithine supplements are available in several forms that are taken by mouth, such as capsules, tablets, and powder. Some products contain ornithine by itself (usually in the form of l-ornithine hydrochloride), while other products combine it with other amino acids or nutrients. Different products may contain different amounts of ornithine.

If you are using ornithine powder, use a kitchen scale or the measuring scoop provided with the product to measure your dose accurately. Read the label carefully and measure the amount stated on the label.

The FDA has not tested ornithine 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 ornithine?

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. 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.

Current and Past Health Conditions. Tell your health care provider if you have any of the following.

  • Liver problems
  • Kidney problems
  • An eye condition known as gyrate atrophy of the choroid and retina
  • Urea cycle disorders or a condition that may cause high ornithine levels in the body

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

Breastfeeding. As a naturally occurring amino acid in the body, ornithine is a normal part of breast milk. However, the safety of taking ornithine supplements while breastfeeding has not been studied. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does ornithine interact with foods or drinks?

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

It is unknown if drinking alcohol will affect ornithine.

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

Overdose/Missed Dose

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

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

Ornithine supplements come in a range of doses and forms, including capsules, tablets, and powder. Read the product label closely and speak to a health care provider about how to use ornithine safely. Do not take double or extra doses, even if you miss a dose.