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Overview: Acetyl-L-carnitine is available over the counter as a supplement and is used for various reasons. However, its benefits are not well defined. Common side effects may include diarrhea, nausea, vomiting, an upset stomach, or a fish-like breath or body odor. Before taking acetyl-L-carnitine, make sure to tell your health care provider about any health conditions you have or medicines you are taking.

Uses

What is acetyl-L-carnitine used for?

Acetyl-L-carnitine is used to increase carnitine levels. It is also used for other reasons, although its benefits are not well defined. Some common reasons that people use acetyl-L-carnitine include the following.

Note: The FDA has not reviewed acetyl-L-carnitine for safety and effectiveness. Learn more about dietary supplements here.

Acetyl-L-carnitine is a form of carnitine. Carnitine is available over the counter as a supplement and also as a prescription medicine. See Levocarnitine for more information about the prescription form of carnitine.

How does acetyl-L-carnitine work (mechanism of action)?

Acetyl-L-carnitine is a form of carnitine, which is an important nutrient. Your body makes carnitine on its own and also gets it from certain foods, such as meat, fish, and dairy. Most of the carnitine in your body is found in your liver and muscles. Your body uses carnitine to make energy from the foods you eat.

Acetyl-L-carnitine is available in dietary supplements and is sometimes used to increase carnitine levels. There is also interest in taking acetyl-L-carnitine for various health problems. But the benefits of taking acetyl-L-carnitine are not well defined. Research has not shown any clear benefits in people with dementia, liver problems, or nerve problems from diabetes. Also, taking acetyl-L-carnitine for nerve problems caused by chemotherapy (peripheral neuropathy) may actually make these problems worse. Acetyl-L-carnitine is not recommended for people who are being treated for cancer.

How should I store acetyl-L-carnitine?

You should store acetyl-L-carnitine according to the product label. Most dietary supplements should be kept in a cool, dry place 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 acetyl-L-carnitine?

The most common side effects of acetyl-L-carnitine are listed below. These side effects may vary, depending on the specific product you are using, and may be more likely with higher doses. Tell your health care provider if you have any of these side effects that bother you.

  • Diarrhea
  • Nausea or vomiting
  • Upset stomach
  • A fish-like smell to your breath, sweat, or urine

There may be other side effects of acetyl-L-carnitine 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 acetyl-L-carnitine?

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

Severe Allergic Reactions. Acetyl-L-carnitine may cause allergic reactions, which can be serious. Stop taking acetyl-L-carnitine 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 acetyl-L-carnitine?

Allergies to Ingredients. People who are allergic to any of the following should not take acetyl-L-carnitine.

  • Acetyl-L-carnitine
  • ALC
  • ALCAR
  • Carnitine
  • L-carnitine
  • Levocarnitine
  • Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific acetyl-L-carnitine products they stock.

What should I know about acetyl-L-carnitine before using it?

Acetyl-L-carnitine 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 acetyl-L-carnitine out of the reach of children.

There are many different forms of carnitine available in dietary supplements, including carnitine (or L-carnitine), acetyl-L-carnitine, and propionyl-L-carnitine. All of these forms increase the levels of carnitine in your body. But your body may absorb each of these forms differently, and it is not clear if dietary supplements are absorbed as well as the carnitine that is found in many foods.

The FDA has not tested acetyl-L-carnitine 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 acetyl-L-carnitine?

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 acetyl-L-carnitine is 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.

Other Medicines and Supplements. Acetyl-L-carnitine may interact with other medicines and supplements. Before taking acetyl-L-carnitine, 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 acetyl-L-carnitine 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 acetyl-L-carnitine passes into breast milk, but carnitine passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does acetyl-L-carnitine interact with foods or drinks?

There are no known interactions between acetyl-L-carnitine and foods or drinks.

It is unknown if drinking alcohol will affect acetyl-L-carnitine.

Does acetyl-L-carnitine 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 receiving chemotherapy, which is a treatment for cancer.

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

Overdose/Missed Dose

What should I do if I accidentally use too much acetyl-L-carnitine?

If you or someone else has used too much acetyl-L-carnitine, 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 acetyl-L-carnitine safely. Do not take double or extra doses, even if you miss a dose.