This information describes the common uses of Carnitine, how it works, and its possible side effects.

Common Name

Vitamin BT, Vitamin B7, ALCAR

How It Works

Some clinical trials show that carnitine supplementation is helpful for patients with angina, heart disease, or peripheral vascular disease. However, guidelines recommend against a particular form, acetyl-l-carnitine, for chemotherapy-induced peripheral neuropathy.

Carnitine is a nutrient found naturally in the body and in foods such as meat and dairy products, beans, and avocados. It plays an important role in energy production by delivering fatty acids that are processed within the cells to be used as fuel. It also helps to prevent damaging effects that can occur when fatty acids build up outside of cells.

L-carnitine is more readily absorbed in the body if obtained from food rather than supplements. However some people, such as those with a genetic deficiency who are fatigued because energy production is greatly reduced, respond well with carnitine supplements. In addition, studies in some patients with heart conditions show improved heart function and ability to exercise after taking carnitine.

There is less evidence for the use of carnitine supplements for other conditions. In clinical trials, cancer patients who have higher blood levels of carnitine generally have higher functioning and more energy. However, one particular form, acetyl-L-carnitine, is known to increase chemotherapy side effects, so it is important to discuss any use of this supplement with your oncologist.

Purported Uses

  • To manage heart disease
    Several clinical trials suggest that carnitine can enhance physical performance, increase exercise tolerance in patients with stable angina, reduce heart damage after a heart attack, and possibly increase survival in patients with heart disease. It may improve circulation in peripheral vascular disease. However, results from one large trial of patients who had a heart attack found no reductions in heart failure events or death with carnitine therapy.
  • To relieve some side effects of chemotherapy
    Data are mixed on whether carnitine helps chemotherapy-related fatigue. In addition, a processed form of carnitine known as acetyl-L-carnitine, has been shown to increase nerve pain. Therefore, additional studies are needed to determine whether carnitine supplementation can benefit cancer patients.
  • To gain weight and prevent weight loss in patients with advanced cancer
    There is some initial evidence that carnitine supplementation may improve nutritional status in patients with advanced pancreatic cancer while improving quality of life. However, additional studies are needed to confirm these effects.
  • To treat chronic fatigue syndrome
    One clinical trial supports this use.
  • To treat diabetes
    In one clinical trial, carnitine given by infusion decreased insulin resistance in patients with type 2 diabetes, but more research is needed to confirm this effect with oral dosages. A few studies also suggest that carnitine may be helpful for diabetic nerve pain.
  • To lower high cholesterol
    Although several clinical trials suggest that carnitine supplements can increase HDL (“good”) cholesterol and reduce blood triglyceride levels, several other clinical trials contradict these findings.
  • To treat infertility
    Studies show mixed results in treating male infertility.
  • To increase strength and stamina
    Studies of oral carnitine for enhanced exercise performance in healthy individuals are poorly designed and show no consistent benefit.
  • To treat Alzheimer’s disease
    Some clinical trials show benefit with a processed form of carnitine known as acetyl-L-carnitine to improve brain function, but two large long-term studies did not find any benefit. In addition, a review of studies on various forms of carnitine to enhance brain function found the current evidence lacking.

Do Not Take If

You are taking warfarin: L-carnitine may increase bleeding risks.

Side Effects

  • Upset stomach
  • Heartburn
  • Flu-like syndrome
  • Sore throat
  • Headache
  • Diarrhea
  • High blood pressure
  • Unpleasant body odor with high doses

Case Report

Low blood sugar: In a patient with a rare genetic metabolic disorder who took carnitine supplements.

Special Point

  • Over-the-counter carnitine supplements may not be well absorbed by the body.
  • L-carnitine may inhibit the action of thyroid hormone, but it is not known whether it interacts with thyroid supplements.
  • L-carnitine should not be confused with acetyl-L-carnitine, which can increase chemotherapy side effects such as nerve pain.