Acetyl L-Carnitine

Acetyl-L-carnitine is a genuinely different product to L-carnitine. These are the questions our naturopaths ask in store, and they're mostly about matching the form to the job.

A good fit if

• You want the carnitine form studied for nerve comfort, not weight or exercise
• Nerve tingling or discomfort is bothering you, and you understand this supports comfort rather than curing anything
• You're an older adult wanting general support for mental function and vitality, alongside a normal diet
• You already take L-carnitine for training and want to know this one is genuinely different

Check with us first if

• Your kidneys aren't working well. Muscle weakness has been reported in people with kidney failure (uraemia).
• You have a seizure disorder. Seizures have been reported with carnitine forms.
• You take valproic acid, phenobarbital, phenytoin or carbamazepine. These medicines lower blood carnitine themselves, so this is one for your prescriber.
• You take a pivalate-containing antibiotic such as pivampicillin, which can run down your carnitine with long-term use.
• You're pregnant or breastfeeding. There's no safety data either way, so we won't guess.

• Acetyl-L-carnitine (ALCAR/ALC, item 350). Best known for: The nerve and brain form, and the one this page's evidence is about. Absorption: Our sources have no head-to-head comparison with L-carnitine, so we won't claim one is absorbed better. Typical use: Nerve comfort and general mental function in older adults, mostly studied in people with diagnosed conditions, which we can't make claims about.
• L-Carnitine, free base (levocarnitine, item 3008). Best known for: The base form, and where the body composition and exercise evidence comes from. Absorption: About 14 to 18 per cent of a supplement dose is absorbed, compared with 63 to 75 per cent of carnitine from food. Typical use: Body weight and fat mass in adults carrying extra weight, and high-intensity training over a long program.
• L-Carnitine L-tartrate (levocarnitine tartrate, item 3012). Best known for: The sports powder version of the same molecule. Absorption: There's no separate absorption data, so treat it as equal to the base form. Typical use: Powders and pre-workouts, because it's stable and absorbs less moisture. It's a formulation choice, not a different action.
• Propionyl-L-carnitine (item 4159). Best known for: The form for circulation to the limbs. Absorption: Not found in our sources. Typical use: Its trials were all in people with a diagnosed disease, so none of it applies to general use.
• D-carnitine, or a label that just says "carnitine". Best known for: The mirror-image molecule your body doesn't use. Absorption: Not applicable. Typical use: Neither is in Schedule 1, so neither is allowed in listed medicines. None of the evidence on this page applies.

Reference values. There's no recommended intake for acetyl-L-carnitine, because healthy adults make their own carnitine and turn some of it into this form.

Typical supplemental range. These are trial doses, not label doses. The nerve and mental function trials we've looked at mostly used 1.5 to 3 g a day, usually split into two doses. A dose of 3 g a day was also tested for 2 months in carpal tunnel syndrome and didn't help there.

Upper level. Not established. There's no upper limit for any form of carnitine, and Australia's permitted ingredients list (item 350) sets no dose cap. Side effects start to show up at around 3 g a day.

Worth knowing. We haven't checked which strengths are sold in Australian stores, so every number here is a trial dose or a regulatory position, not a label recommendation. What you need depends on your age, diet and health, so talk to one of our naturopaths.

Food first, where the diet allows it.

• Beef steak, cooked, 85 g: 42 to 122 mg carnitine, the raw material your body draws on
• Ground beef, cooked, 85 g: 65 to 74 mg carnitine
• Whole milk, 1 cup: 8 mg carnitine
• Chicken breast, cooked, 85 g: 2 to 4 mg carnitine
• Asparagus, cooked, half a cup: 0.1 mg, and a whole vegan day comes to about 1.2 mg

If any of these sound like you, talk to one of our naturopaths or your doctor before you start.

• Kidney failure. Muscle weakness has been reported in people with uraemia.
• Seizure disorders. Seizures have been reported in people who have them.
• Epilepsy medicines. Valproic acid, phenobarbital, phenytoin and carbamazepine all lower blood carnitine themselves, so you'll need medical supervision.
• Antibiotics such as pivampicillin (pivalate-conjugated). Long-term use can deplete carnitine.
• Cancer treatment. Guidelines specifically advise against acetyl-L-carnitine to prevent nerve damage from chemotherapy.
• Pregnancy and breastfeeding. We found no data either way, so we won't give guidance we don't have.
• Around 3 g a day and above. Some people get nausea, headache or stomach upset.