Compare L-carnitine products on the amount of carnitine per daily serving, the form (L-carnitine, L-carnitine L-tartrate or acetyl-L-carnitine), the format and the cost per gram. L-carnitine has no authorised health claims in Great Britain, and the evidence for weight loss is weak, so we set out what's known before you buy.
All weight management · Fat burners · Thermogenics · Diet & lean protein · Amino acids
Filters
Clear all
What is L-carnitine?
L-carnitine is a compound your body makes and that you also get from food, mainly meat and other animal products. The US National Institutes of Health says the liver and kidneys make enough carnitine to meet daily needs in healthy people, so most people don't need it from supplements.
It plays a part in moving fatty acids into the parts of cells that use them for energy, which is why it's often marketed for dieting. That role in the body doesn't mean taking more of it as a supplement changes how much fat you use.
What does L-carnitine do as a supplement?
There are no authorised health claims for L-carnitine in Great Britain, so no product can legally say it does anything for your body. EFSA, the European food safety authority, assessed a claim that L-carnitine contributes to normal lipid (fat) metabolism and concluded that a cause and effect relationship has not been established.
"Where evidence is limited or inconclusive, we should say so openly," says Andy Arshad, who runs SupplementHQ. For sports use, the NIH says research findings on carnitine and athletic performance are mixed.
Does L-carnitine help with weight loss?
The evidence suggests any effect is small. The NIH says carnitine supplements might help you lose a small amount of weight, and its fact sheet for health professionals reports one 2016 analysis where people taking carnitine lost an average of 1.33kg more than those taking a placebo, noting that larger studies are needed.
We don't claim any product here causes weight loss. The NHS advice is to aim to lose 0.5 to 1kg (1 to 2lbs) a week through diet and activity. See weight management for more.
L-carnitine vs acetyl-L-carnitine: what's the difference?
They're different forms of carnitine. Acetyl-L-carnitine (often shortened to ALCAR) has an acetyl group attached, and L-carnitine L-tartrate is carnitine bound to tartaric acid. Because each form contains a different proportion of carnitine by weight, 1g of one isn't the same amount of carnitine as 1g of another.
This collection includes plain L-carnitine, acetyl-L-carnitine and blends with green tea or CLA. Check which form is listed on the label and compare like with like.
Liquid, capsules or shots?
Choose the format you'll actually use, then compare the amount of carnitine per serving and the cost per gram. Liquids and shots are convenient, but they can contain sweeteners or sugars and often cost more per gram than capsules.
"We think customers should compare the actual amount of active ingredients they're getting, rather than just the format or marketing," says Andy.
| Format | What to check |
|---|---|
| Capsules or tablets | Carnitine per capsule and how many make one serving |
| Liquid bottles | Carnitine per measured serving (often per 10ml or 20ml) and servings per bottle |
| Single shots | Carnitine per shot, any added caffeine and the cost per shot |
| Blends | The separate amount of each ingredient, not just a blend total |
How to compare value (example figures, not real products): a £15 tub of 100 capsules with 1g of L-carnitine per capsule costs 15p per gram. A £3 shot with 3g costs £1 per gram, nearly seven times as much for the same amount of carnitine.
What are the side effects of L-carnitine?
At around 3g a day, the NIH says carnitine can cause nausea, vomiting, stomach cramps, diarrhoea and a fishy body odour. Gut bacteria can also turn carnitine into a compound called TMAO, which researchers are studying for links with heart disease; the NIH says the implications are not yet well understood.
Some medicines, including certain epilepsy medicines, affect carnitine levels. Speak to your GP or pharmacist before taking carnitine if you have a medical condition such as kidney disease or a seizure disorder, take medication, or are pregnant or breastfeeding.
Is L-carnitine worth it?
That depends on what you expect from it. Most healthy people make enough of their own, there are no authorised claims, and the weight-loss effect seen in studies is small.
If you still want to try it, compare the form, the amount per serving and the cost per gram, and check whether a blend also contains caffeine. Our guide to what supplements you actually need is a good place to start.
We sell the products on this page. That's our commercial interest, and it's why we show the evidence alongside them. This page is general information for adults, not personalised medical advice. Food supplements should not replace a varied, balanced diet.
Written by Andy Arshad, SupplementHQ. Last reviewed 11 October 2026.