What is carnitine deficiency?

Carnitine is a natural substance that the body uses to process fats and produce energy. Carnitine deficiency is when not enough (less than 10%) of the nutrient carnitine is available to cells in the body. This can cause muscle weakness and heart or liver problems.

You get carnitine through some of the foods you eat. It plays an important role in getting fatty acids into cells to use for energy. Carnitine is especially important for certain cells, such as muscle cells. With carnitine deficiency, cells that need fatty acids for energy may start to work poorly. Carnitine deficiency can happen in children and adults of all ages and all ethnic backgrounds.

There are 2 types of carnitine deficiency:

• Primary carnitine deficiency. This is a rare condition caused by an abnormal gene. The gene causes a problem with a substance that carries carnitine inside cells from the blood. In some cases, the condition only leads to low carnitine levels in muscle. This is called primary muscle carnitine deficiency. In this condition, the body can't use certain fats for energy, especially when the person goes without food (fasting). If the liver and heart are also affected, it may be called systemic carnitine deficiency. It is also called carnitine uptake defect.

• Secondary carnitine deficiency. This is a more common condition. In this case, there isn’t a problem getting carnitine into cells. Instead, the problem is that there isn’t enough carnitine in the blood. It can result from a number of health problems.

What causes carnitine deficiency?

The primary condition is caused by an abnormal gene. 

Different health conditions can cause the secondary condition. These decrease the amount of carnitine in the body. They may do this by increasing the amount sent out in urine. Or they may cause the body to absorb less from food. The health problems that can cause this include:

• Liver disease

• Kidney disease, especially with dialysis

• Digestive disease that causes poor absorption

• Malnutrition

• Mitochondrial disease

• Certain metabolic disorders

• Certain medicines, such as valproate

Who is at risk for carnitine deficiency?

The primary condition is passed down from parents to children. A child needs to get an abnormal copy of the gene from both parents.

You may have a risk for the secondary condition if you have liver or kidney disease, or certain other health conditions.

What are the symptoms of carnitine deficiency?

The primary condition leads to more severe symptoms than the secondary condition. Children with primary carnitine deficiency tend to show symptoms within the first few years of life. But in some cases, symptoms may start as an adult.

Symptoms can happen a bit differently in each person. You may have no symptoms, or your symptoms may be mild to severe. Some symptoms may appear with skipping meals, a lot of exercise, or illness. Symptoms can include:

• Decreased or floppy muscle tone or muscle weakness

• Tiredness (fatigue)

• Irritability

• Delayed movement (motor) development

• Poor feeding in a baby

• Symptoms of low blood sugar (hypoglycemia) if the liver is affected

• Swelling (edema) or shortness of breath, if the heart is affected

The symptoms of carnitine deficiency can be like other health conditions. Make sure to see your healthcare provider for a diagnosis.

How is carnitine deficiency diagnosed?

The condition may be diagnosed by a neurologist or geneticist. An infant may be diagnosed during standard newborn screening tests.

The process to diagnose carnitine deficiency starts with a health history and a physical exam. Your healthcare provider will ask about your symptoms and past health conditions. They may also ask about your family’s health history. The physical exam may include a neurological exam. Tests may also be done. These include:

• Blood tests. These check the levels of carnitine in the blood. They also check for creatine kinase. This shows muscle damage. And they check for enzymes in the blood that can show liver disease.

• Urine test. This test looks for a protein called ketones.

• Exercise tests. These help identify the type of metabolic problem.

• Genetic test. This kind of test can confirm primary carnitine deficiency.

• Heart tests. Tests such as echocardiography can show if the heart is affected.

How is carnitine deficiency treated?

The main treatment for this condition is to take L-carnitine supplements. This is the usable form of carnitine. It is available in pill form. L-carnitine increases the amount of carnitine in the blood and inside cells. This can help prevent many of the symptoms of the disease.

If you have the primary condition, you will probably need to take L-carnitine for the rest of your life. If you have the secondary condition, you may only need to take carnitine for a limited time. You may need repeated blood tests to check your carnitine levels.

If you have heart and liver problems, these may need other treatment.

It’s also important to stay away from things that may trigger symptoms. These include skipping meals, exposure to cold, and a lot of exercise.

What are possible complications of carnitine deficiency?

Heart weakness is a serious possible complication. A weakened heart may not be able to pump blood as well. This can lead to symptoms such as swelling and shortness of breath. Untreated heart weakness may lead to death early in life. Fortunately, heart problems respond very well to treatment with L-carnitine. Your healthcare provider may want to continue to monitor your heart for signs of weakness. Heart problems may be the first symptom of carnitine deficiency.

Liver problems are another serious possible complication. They often affect children in the first few years of life. The liver may enlarge and not work as well as it should. This may cause problems such as poor feeding and irritability in the baby. Liver problems can lead to episodes of hypoglycemia. Infections are often the trigger for these episodes. Severe hypoglycemia can lead to coma and death if not treated right away with a sugar called dextrose.

Liver problems may or may not respond well to treatment with L-carnitine. These liver problems may also be the first symptoms of a carnitine deficiency.

What can I do to prevent carnitine deficiency?

If the condition runs in your family, you may want to see a genetic specialist before you have a baby. Genetic testing can be done to find out your risk of passing the disease to your child.

If you do have the abnormal gene for the condition, you have options. If you use in vitro fertilization, the embryos can be tested for the disease. Amniocentesis can also be used to test for the condition in early pregnancy.

Carnitine is found in red meat, chicken, and fish, and also in milk.

Key points about carnitine deficiency

• Carnitine deficiency is a condition where the nutrient can’t reach your body’s cells. It can cause muscle weakness. It may also cause heart and liver problems.

• With the primary condition, not enough carnitine can get into cells because of a genetic problem. With the secondary condition, carnitine is low for other health reasons.

• If the condition runs in your family, you may want to see a genetic specialist before you have a baby.

• L-carnitine supplements are the main treatment. They work well to treat many symptoms.

• If untreated, carnitine deficiency can lead to serious heart and liver complications.

• You may need to avoid activities than can trigger symptoms, such as skipping meals or a lot of exercise.

Next steps

Tips to help you get the most from a visit to your healthcare provider:

• Know the reason for your visit and what you want to happen.

• Before your visit, write down your questions.

• Bring someone with you to help you ask questions and remember what your provider tells you.

• At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

• Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.

• Ask if your condition can be treated in other ways.

• Know why a test or procedure is advised and what the results could mean.

• Know what to expect if you do not take the medicine or have the test or procedure.

• If you have a follow-up appointment, write down the date, time, and purpose for that visit.

• Know how you can contact your provider if you have questions.