Carnitine, which includes the compounds L-carnitine, acetyl-L-carnitine, and propionyl-L-carnitine is a natural substance derived from an amino acid. In most people, the body produces enough carnitine.
Carnitine plays an important role in energy production un the body. It helps get fatty acids into cells to use for energy. Carnitine is concentrated in skeletal tissue and heart muscle that use fatty acids as dietary fuel.
Carnitine is a drug approved by the Food and Drug Administration (FDA) to treat primary and certain secondary carnitine-deficiency syndromes.
L-carnitine, acetyl-L-carnitine, and propionyl-L-carnitine are available over-the-counter (OTC) as dietary supplements and are often touted as aids for weight loss, improving exercise performance, and enhancing well-being.
Carnitine may be helpful for:
- Aging
- Improving mental function in older adults with mild cognitive impairment and Alzheimer’s disease
- Cardiovascular and peripheral arterial disease
- Fatigue resulting from chemotherapy, radiation treatment, and poor nutrition in cancer patients
- Type 2 diabetes
- Human immunodeficiency virus (HIV) and acquired immunodeficiency syndrome (AIDS)
- Anemia management in end-stage renal disease and hemodialysis
There is no evidence to support the use of carnitine for the following conditions:
- Athletic performance
- Male infertility
Talk to your doctor before taking carnitine supplements.
What Is the Recommended Intake for Carnitine?
Healthy adults and children do not need carnitine supplementation because the liver and kidneys make enough from the amino acids lysine and methionine to meet daily needs.
The Food and Nutrition Board of the National Academies (formerly National Academy of Sciences) concluded in 1989 that it was not an essential nutrient and they have not established a recommended dietary allowance (RDA) for carnitine.
What Are Side Effects of Carnitine Supplements?
At doses of approximately 3 g/day, side effects of carnitine supplements may include:
What Foods Contain Carnitine?
Carnitine occurs in two forms, known as D and L, but only L-carnitine is active in the body and is the form found in food.
Foods that contain carnitine include:
- Animal products contain the most carnitine
- Meat, such as beef
- In general, the redder the meat, the higher its carnitine content
- Fish such as cod
- Poultry such as chicken
- Dairy products
- Dairy products contain carnitine primarily in the whey
- Milk
- Cheddar cheese
- Ice cream
- Meat, such as beef
- Whole wheat bread
- Asparagus
Adults who consume red meat and other animal products get about 60–180 milligrams of carnitine per day. Vegans get about 10–12 milligrams since they do not consume animal-derived foods, however, carnitine is efficiently conserved by the kidneys so even diets that have little carnitine have a minimal impact on the body’s total carnitine content. Any excess carnitine passes out of the body in urine to maintain stable blood concentrations.
What Causes Carnitine Deficiency?
There are two types of carnitine deficiency:
- Primary carnitine deficiency
- A genetic disorder
- Usually develops by five years of age
- Symptoms include
- Disease of the heart muscle (cardiomyopathy)
- Skeletal-muscle weakness
- Low blood sugar (hypoglycemia)
- Secondary carnitine deficiency
- Caused by other underlying conditions that decrease the amount of carnitine in the body that cause the body to:
- Increase the amount of carnitine excreted in urine
- Absorb less carnitine from food
- Chronic renal failure
- Use of certain antibiotics
- Certain medicines, such as valproate
- Liver disease
- Digestive disease that causes poor absorption
- Malnutrition
- Mitochondrial disease
- Certain metabolic disorders
- Caused by other underlying conditions that decrease the amount of carnitine in the body that cause the body to:
From 
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https://ods.od.nih.gov/factsheets/Carnitine-HealthProfessional/