At a glance
Effects
- Fat oxidation / energy production: Transports long-chain fatty acids into mitochondria for beta-oxidation, directly supporting fat burning and ATP generation [4][2].
- Exercise recovery: L-carnitine L-tartrate (LCLT) is the form most commonly studied for exercise performance; it may reduce muscle soreness and oxidative damage post-training [1].
- Metabolic & liver health: Supplementation has been shown to reduce markers of liver inflammation (AST, ALT) and triglycerides, and to support glucose metabolism in individuals with impaired glucose tolerance [5][1].
- Cognitive / neurological support: Acetyl-L-carnitine (ALCAR), the acetylated form, crosses the blood-brain barrier more readily and is studied for neuropathy, depression, and dementia support [1].
- Sperm quality: Evidence suggests L-carnitine supplementation may improve some aspects of sperm motility and male reproductive health [1].
Amino acid derivative / conditionally essential nutrient
Oral (capsule, powder, liquid); IV (prescription only)
~14–18% (oral supplement form) [4]
Unscheduled; available OTC as supplement; prescription (Carnitor) for deficiency
TMAO — cardiovascular risk signal at high doses [7][11]
About L-Carnitine
Every point here is drawn from public medical and harm-reduction sources. A bracketed number after a claim — like [1]— is a reference: tap it to open the exact source it's based on (numbered list at the bottom). It is not a rating or score. Educational information, not medical advice.
Product specifics
- Est. delivery
- 3–7 business days · EU tracked
Product details as stated by the vendor (claims, not independently verified). Delivery is our standard EU estimate.
What it is
L-Carnitine (levocarnitine) is a naturally occurring quaternary ammonium compound and amino acid derivative produced in the brain, liver, and kidneys from the amino acids lysine and methionine [3][4]. It is used clinically to treat carnitine deficiency and is widely supplemented for fat metabolism, exercise performance, and metabolic health support [1].
How it works
L-Carnitine's primary role is shuttling long-chain fatty acids across the inner mitochondrial membrane so they can be broken down via beta-oxidation to produce cellular energy [4][2]. It also helps remove excess acetyl-CoA from the mitochondrial matrix, preventing inhibition of pyruvate dehydrogenase (PDH) and thereby sustaining efficient aerobic energy production [2]. Additionally, it exhibits antioxidant properties and may act as an endogenous HDAC inhibitor, with emerging roles in metabolic and liver health [1][6].
Risks & side effects
Most important: Gut bacteria can convert supplemental L-carnitine into trimethylamine-N-oxide (TMAO), a metabolite associated with increased risk of atherosclerosis, heart attack, and stroke — particularly at higher doses [7][11]. Individuals with pre-existing cardiovascular risk factors should consult a physician before supplementing.
Common
Serious
- Elevated TMAO levels: gut bacteria convert carnitine to TMAO, which is linked to atherosclerosis, heart attack, and stroke risk [7][11]
- Exacerbation of hypothyroidism symptoms: L-carnitine may inhibit thyroid hormone action and worsen underactive thyroid [8][12]
- Potentiation of anticoagulants (warfarin, acenocoumarol): may increase bleeding risk; INR monitoring required [8]
- Seizures reported as a rare but documented side effect, particularly in predisposed individuals [8][9]
Safety & harm reduction
- History of seizure disorder — L-carnitine may increase seizure risk [8]
- Diagnosed hypothyroidism — carnitine may worsen symptoms of underactive thyroid [8][12]
- Avoid D-carnitine or DL-carnitine forms — these can block L-carnitine activity [8]
- Pregnancy — insufficient safety data; avoid unless directed by a physician [8]
- Warfarin / acenocoumarol: L-carnitine may increase anticoagulant effect; bleeding risk elevated [8]
- Thyroid hormone medications (levothyroxine, etc.): L-carnitine may reduce effectiveness [8][12]
- Valproic acid (anticonvulsant): alters carnitine metabolism; L-carnitine is used to counteract valproate toxicity but combined use needs medical supervision [4]
- Certain antibiotics: may affect carnitine levels; consult a physician [8]
- Take with food to reduce gastrointestinal side effects [1][7]
- Keep supplemental doses at or below 2 g/day for general wellness; doses above 3 g/day markedly increase GI side effects and TMAO risk [7][11]
- Choose L-carnitine L-tartrate (LCLT) for exercise/recovery purposes; acetyl-L-carnitine (ALCAR) for cognitive applications [1]
- Vegans and vegetarians may have lower baseline carnitine levels and could benefit more from supplementation [10]
Dosage context
Commonly reported oral supplement doses range from 500 mg to 2,000 mg per day; up to 2,000 mg/day is considered safe for most healthy adults [1][2]. Doses up to 6 g/day have been used in clinical trials, but 3 g/day and above is the threshold where nausea, vomiting, and fishy odour become likely [7]. L-carnitine L-tartrate doses of 1,000–4,500 mg/day are reported in exercise performance contexts [10]. These are commonly reported ranges, not a prescription — consult a healthcare provider for personalised guidance.
Sources
- 1.Examine.com — L-Carnitine benefits, dosage, and side effects
- 2.NIH Office of Dietary Supplements — Carnitine Health Professional Fact Sheet
- 3.DrugBank — Levocarnitine (DB00583)
- 4.PMC — L-carnitine for valproic acid-induced toxicity (bioavailability data)
- 5.PMC — Liver Lipidomics Analysis: L-Carnitine on NAFLD
- 6.PMC — L-Carnitine as endogenous HDAC inhibitor
- 7.ScienceInsights — Is L-Carnitine Safe? Dosage, Risks, and Side Effects
- 8.WebMD — L-Carnitine Overview, Uses, Side Effects, Interactions
- 9.WebMD Drugs — Levocarnitine (Carnitor) drug detail
- 10.Healthline — L-Carnitine Benefits, Side Effects, Sources, and Dosage
- 11.PMC — L-Carnitine cardiovascular risk / TMAO meta-analysis
- 12.Rupa Health — L-Carnitine and Hypothyroidism
This information is provided for educational and harm-reduction purposes only. It is not medical advice. These substances can carry serious health risks; effects and safe use vary by individual. Consult a qualified healthcare professional before use. Legal status varies by country — it is your responsibility to know your local law. We do not encourage misuse.
Other options for L-Carnitine· 2 offers
Same compound from different labs/brands and pack sizes. Tap a row to switch brand — the price and buy button update instantly.
| Brand | Form | Strength | Pack | Price | Per mg |
|---|---|---|---|---|---|
Generic | vial | 500 mg/ml | 10 ml | 27,90 € | ★€0.006/mg |
GenericSelected | vial | 500 mg/ml | 100 ml | 299,99 € | €0.006/mg |