L-Carnitine (Levocarnitine), also called levocarnitine (and sold as a supplement under the name L-carnitine), is a natural substance your body makes from two protein building blocks, lysine and methionine. You also get it from foods such as meat, fish and milk. The body needs it to turn fat into energy. As a medicine, L-Carnitine (Levocarnitine) is used to treat carnitine deficiency, which means having too little carnitine in the body. This can happen because of an inherited condition, certain inherited metabolic disorders (conditions in which the body cannot break down some foods properly) or long-term kidney dialysis (a treatment that filters the blood when the kidneys have failed). By refilling the body's carnitine supply, L-Carnitine (Levocarnitine) helps cells, especially in the muscles and heart, get the energy they need.

Every cell needs energy, and a large share of it comes from burning fat. That burning happens inside tiny energy units in the cell called mitochondria. Long-chain fats cannot get into the mitochondria by themselves. L-Carnitine (Levocarnitine) works like a shuttle that carries these fats inside so they can be burned for fuel. It also helps carry certain harmful waste products out of the mitochondria so the body can pass them out in the urine.

Most healthy people make enough carnitine and get the rest from food. Some people do not. In primary carnitine deficiency, an inherited problem stops cells from taking in and holding on to carnitine. This can cause muscle weakness, low blood sugar, heart muscle problems and tiredness, often starting in childhood. Secondary carnitine deficiency can happen with some inherited metabolic disorders, long-term kidney dialysis, or treatment with certain medicines such as valproic acid. In each case, L-Carnitine (Levocarnitine) is given to bring carnitine levels back up.

L-Carnitine (Levocarnitine) comes as tablets and as an oral solution (a liquid you drink). There is also an injection, given in hospital. People on long-term dialysis receive the injection from their dialysis team after dialysis sessions, rather than the tablets or liquid. The liquid is useful for children and for people who find tablets hard to swallow.

L-Carnitine (Levocarnitine) is also sold as a dietary supplement. Researchers have studied it for heart health, male fertility, exercise performance and weight loss, but the results so far have been mixed. When L-Carnitine (Levocarnitine) is used to treat a diagnosed deficiency, a doctor should decide the dose and keep an eye on progress. This matters most for people with kidney disease, seizures or an underactive thyroid, and for those taking blood thinners. Large amounts can upset the stomach and cause a fishy body odour, so do not take more than your doctor advised.

1. Refills low carnitine levels - L-Carnitine (Levocarnitine) brings carnitine back up in people with primary or secondary carnitine deficiency.
2. Supports energy from fat - It helps carry fats into the cells' energy units, which is especially helpful for muscles and the heart.
3. Helps clear harmful waste - It binds to certain harmful substances that build up in some inherited metabolic disorders and helps the body pass them out in the urine.
4. Used during long-term dialysis - People with kidney failure on dialysis can lose carnitine. For them, L-Carnitine (Levocarnitine) is given as an injection by the dialysis team after dialysis sessions. The tablets and liquid are not recommended for long-term use in people on dialysis.
5. Flexible forms - Tablets, an oral solution and an injection let doctors choose what suits adults, children and hospital patients.

Common Side Effects (Usually Mild)

• Nausea
• Vomiting
• Stomach cramps or pain
• Diarrhoea
• A fishy smell on the body, breath or urine. This happens when gut bacteria break L-Carnitine (Levocarnitine) down into a substance called trimethylamine. It is more likely at higher doses.

Taking the dose with food, or diluting the liquid more and sipping it slowly, may ease stomach upset.

Serious Side Effects (Seek Urgent Medical Attention)

• Seizures (fits), in people with or without a history of seizures
• Unusual bruising or bleeding, especially if you take a blood thinner such as warfarin
• Signs of a serious allergic reaction, such as rash, hives, swelling of the face, lips or throat, or trouble breathing

• Take L-Carnitine (Levocarnitine) exactly as your doctor has prescribed. It is usually taken two or three times a day.
• Take it with a meal or just after one. This helps reduce stomach upset.
• Swallow tablets with a glass of plain water. Unless your doctor or the pack says you can, do not crush, chew or break them.
• You can drink the oral solution on its own or mix it into a drink or liquid food. Sip it slowly instead of gulping it, because this makes stomach upset less likely.
• Measure the liquid with the measuring cup or syringe that comes with it, not a kitchen spoon.
• Space your doses evenly through the day, usually about every 3 to 4 hours while you are awake, and take them at the same times each day.
• Keep taking L-Carnitine (Levocarnitine) for as long as your doctor advises, even if you feel well. Deficiency conditions often need long-term treatment.

Inside each cell are tiny energy units called mitochondria, which burn fuel to make energy. Long-chain fatty acids (the main kind of fat in the body) cannot cross into the mitochondria by themselves.

L-Carnitine (Levocarnitine) solves this by acting as a carrier. An enzyme (a protein that speeds up a chemical reaction) attaches the fat to L-Carnitine (Levocarnitine). This joined form can pass through the inner wall of the mitochondria. Once inside, the fat is released and broken down for energy in a process called beta-oxidation, and L-Carnitine (Levocarnitine) goes back out to pick up more fat. This back-and-forth is often called the "carnitine shuttle".

L-Carnitine (Levocarnitine) has a second job too. In some inherited metabolic disorders, harmful acid-type compounds build up in the cells. L-Carnitine (Levocarnitine) attaches to them and forms substances that can leave the cell and pass out in the urine. This lowers the toxic load and frees up the cell's own energy machinery.

When carnitine is low, fat cannot be used properly, so muscles and the heart may get weak and blood sugar can drop. Taking L-Carnitine (Levocarnitine) restores the supply so the shuttle can work again.

• Take L-Carnitine (Levocarnitine) with or just after meals to protect your stomach.
• If you take the liquid, mix it into a drink and sip slowly.
• If a fishy body odour shows up, tell your doctor. A dose change may help, but do not change the dose yourself.
• Avoid products labelled "D-carnitine" or "DL-carnitine". These forms can block the effect of L-carnitine.
• If you take warfarin, have your INR (a blood clotting test) checked as often as your doctor advises.
• If you are on dialysis, do not start the tablets or liquid on your own. Your care team will decide on the injection if you need it.
• Tell your doctor right away if you have a seizure or notice unusual bruising or bleeding.

• Store at room temperature, ideally around 25°C (77°F), or as stated on your pack. Short periods between 15°C and 30°C (59°F and 86°F) are acceptable. Keep it away from heat and moisture.
• Do not keep it in the bathroom or anywhere damp.
• Keep the container tightly closed and away from direct sunlight.
• Keep it out of sight and reach of children and pets.
• Do not use it after the expiry date. Ask your pharmacist how to throw away unused medicine safely.

• Meals - Taking L-Carnitine (Levocarnitine) with or just after food helps reduce nausea and stomach cramps.
• Carnitine-rich foods - Red meat, fish, poultry and milk naturally contain carnitine. You do not need to avoid them, but tell your doctor about any big change in your diet.
• Alcohol - Alcohol may make stomach side effects worse.

• Warfarin and acenocoumarol (blood thinners) - L-Carnitine (Levocarnitine) may make these medicines work more strongly, which can raise the risk of bruising and bleeding. Your doctor may check your INR more often.
• Thyroid hormone (such as levothyroxine) - L-Carnitine (Levocarnitine) may reduce the effect of thyroid hormone in the body.
• Valproic acid (sodium valproate) - This seizure medicine can lower carnitine levels in the body. Doctors sometimes give L-Carnitine (Levocarnitine) for this reason, so let them guide its use.
• Pivalate-containing antibiotics (such as cefditoren pivoxil or pivmecillinam) - These can lower carnitine levels, especially with long-term use, which may reduce the benefit of L-Carnitine (Levocarnitine). Tell your doctor if you are prescribed one of them.
• D-carnitine or DL-carnitine products - These forms can block the effects of L-Carnitine (Levocarnitine) and should be avoided.

Tell your doctor and pharmacist about every medicine, supplement and herbal product you take.

• Seizure disorders (epilepsy) - L-Carnitine (Levocarnitine) may make seizures more likely or more frequent in people who have had seizures before.
• Underactive thyroid (hypothyroidism) - L-Carnitine (Levocarnitine) might make the symptoms of an underactive thyroid worse.
• Kidney failure - In severe kidney disease or on dialysis, long-term high doses of the tablets or liquid can let potentially harmful breakdown products (trimethylamine and trimethylamine-N-oxide) build up. People on dialysis are usually given L-Carnitine (Levocarnitine) as an injection, with the dose set by their care team.
• Bleeding problems or blood thinner use - Because L-Carnitine (Levocarnitine) may change how warfarin works, people with bleeding problems need careful monitoring.

Your doctor decides the dose of L-Carnitine (Levocarnitine) based on your condition, age, body weight, kidney function and how well you respond. Typical doses are:

• Adults (tablets) - 990 mg two or three times a day.
• Adults (oral solution) - 1 to 3 g a day, started low and increased slowly.
• Infants and children - 50 to 100 mg per kg of body weight a day, split into smaller doses, up to 3 g a day.
• People on dialysis - The dialysis team sets the injection dose and gives it after each session.

Doses are usually split through the day and taken with meals. Supplement amounts of about 3 grams a day have been linked to nausea, vomiting, stomach cramps, diarrhoea and a fishy body odour. Your own dose may differ, so always follow your doctor's prescription. Never take more than prescribed, and do not change your dose or stop L-Carnitine (Levocarnitine) without talking to your doctor.

Taking too much L-Carnitine (Levocarnitine) mainly causes stomach and gut symptoms, such as:

• Severe diarrhoea
• Nausea and vomiting
• Stomach cramps
• A strong fishy body odour

People with a history of seizures or with kidney failure may be at higher risk of more serious effects. If you think someone has taken too much, get medical help right away or go to the nearest emergency department. Take the medicine pack with you.

If you miss a dose of L-Carnitine (Levocarnitine), take it as soon as you remember, ideally with food. If it is almost time for your next dose, skip the missed one and carry on with your usual schedule. Do not take a double dose to make up for a missed one.

Contact your doctor or get emergency help if you notice:

• A seizure (fit), even if you have never had one before
• Rash, hives, swelling of the face, lips, tongue or throat, or trouble breathing
• Unusual bruising or bleeding, especially if you take warfarin
• Ongoing vomiting or diarrhoea that stops you from keeping fluids down
• Symptoms of carnitine deficiency coming back, such as extreme tiredness, weakness or signs of low blood sugar (shakiness, sweating, confusion)