Compare prices and buy L-Carnitine from 16 research peptide vendors - also called suppliers or sources. Updated daily.
L-carnitine (levocarnitine, CAS 541-15-1, C7H15NO3) is a small quaternary ammonium compound that the body makes from lysine and methionine. It is not a peptide. It carries long-chain fatty acids across the inner mitochondrial membrane for beta-oxidation. As levocarnitine (Carnitor and generics) it is an FDA-approved drug for carnitine deficiency, and it is also sold in the US as a dietary supplement. Gut bacteria convert ingested L-carnitine to TMAO, and in atherosclerosis-prone mice this pathway increased atherosclerosis. Research-vendor listings include ready-to-use liquids and vials labelled by mass.
For research purposes only. Not medical advice.
L-carnitine is not a peptide. It is a small quaternary ammonium compound that the body makes from two amino acids. Methyltransferases add methyl groups from S-adenosylmethionine, made from methionine, to lysine residues in proteins, and the freed trimethyllysine is converted to carnitine in four steps. The last enzyme sits in the kidney, liver and brain, so heart and skeletal muscle rely on taking carnitine up from the blood (Longo, Biochimica et Biophysica Acta, 2016). Most dietary carnitine comes from animal foods, and the NIH Office of Dietary Supplements states that healthy children and adults make enough to meet their needs.
CAS 541-15-1 is levocarnitine, the L form, which the FDA label describes as an inner salt (C7H15NO3, molecular weight 161.2). D-carnitine, DL-carnitine, acetyl-L-carnitine, propionyl-L-carnitine and L-carnitine L-tartrate are separate substances with their own CAS numbers.
PeptideScouter catalogues it under Mitochondrial because research-peptide vendors sell it from the same catalogs as MOTS-c and SS-31, and because some versions of Lipo-C include it. It shares no chemistry with those peptides.
Long-chain fatty acids cannot cross the inner mitochondrial membrane on their own. Carnitine palmitoyltransferase 1 (CPT1), on the outer membrane, moves the fatty acyl group from coenzyme A onto carnitine, a step malonyl-CoA inhibits. The carnitine-acylcarnitine translocase carries the acylcarnitine across the inner membrane, where CPT2 hands the acyl group back to coenzyme A for beta-oxidation, whose dehydrogenase steps reduce FAD and NAD+ (Longo, 2016).
Heart and muscle cells take carnitine up through the transporter OCTN2, which the kidney also uses to reabsorb it. Mutations in its gene, SLC22A5, cause primary systemic carnitine deficiency (Nezu, Nature Genetics, 1999). Carnitine also binds acyl groups that build up in some inherited organic acidemias, and the resulting acylcarnitines leave in urine, the basis the label gives for its use there.
Levocarnitine holds current US approvals, so the bulks-list process that settles most research compounds' status is not where its status is decided.
Section 503A of the FD&C Act requires a bulks-list entry only for substances that lack both a USP monograph and a place in an approved drug, and levocarnitine is the active ingredient of the drugs above. FDA's 503B list (updated March 21, 2025) holds it in Category 1, under evaluation, marked as a component of approved drugs. No carnitine form appears on FDA's Category 2 safety-risk page. L-carnitine is also sold as a dietary supplement, and the drug approvals do not extend to research-vendor products.
Outside deficiency, research has mostly tested oral supplements, and the labels put oral levocarnitine's absolute bioavailability at about 15 percent. The Office of Dietary Supplements describes the exercise results as mixed and the weight results as equivocal, with weight a secondary outcome in most of those trials.
A widely cited adverse finding comes from Koeth and colleagues (Nature Medicine, 2013). In atherosclerosis-prone Apoe-deficient mice, dietary L-carnitine raised gut-microbial production of trimethylamine and its oxidized form, TMAO, and increased atherosclerosis, which did not happen when antibiotics suppressed the gut bacteria. In a challenge test, omnivores given oral L-carnitine made more TMAO than vegans or vegetarians. In an observational cohort of 2,595 people undergoing elective cardiac evaluation, plasma L-carnitine predicted cardiovascular disease and events only among those who also had high TMAO, an association that cannot show cause. The Carnitor labels list TMAO as a major metabolite of oral carnitine.
A 2022 placebo-controlled trial of oral L-carnitine in 157 adults with metabolic syndrome found no difference in its primary outcome, carotid plaque volume, after six months. Carotid stenosis and LDL cholesterol, secondary measures, rose more on L-carnitine (Johri, Nutrition and Metabolism).
No. L-carnitine is a small quaternary ammonium compound, C7H15NO3, that the body makes from the amino acids lysine and methionine, with the final step in the kidney, liver and brain. It carries long-chain fatty acids into mitochondria for oxidation. PeptideScouter catalogues it with the mitochondrial compounds because research-peptide vendors sell it from the same catalogs and because some Lipo-C mixtures include it. It shares no chemistry with the peptides in that category.
Yes, as levocarnitine. Carnitor's oral forms were approved in 1985 and 1986 and its injection in 1992, and generic versions followed. The oral label covers primary systemic carnitine deficiency and secondary carnitine deficiency caused by inborn errors of metabolism. The injection label covers the inborn-error indication and, since 1999, the prevention and treatment of carnitine deficiency in patients with end-stage renal disease on dialysis. L-carnitine is also sold in the US as a dietary supplement. The approvals cover those labelled drug products and do not extend to research-vendor liquids or vials.
They are distinct substances with their own CAS numbers. L-carnitine itself is 541-15-1, its mirror image D-carnitine is 541-14-0, and the racemic DL form is 406-76-8. Acetyl-L-carnitine (3040-38-8) carries an acetyl group on the hydroxyl, and propionyl-L-carnitine (20064-19-1) a propionyl group. L-carnitine L-tartrate (36687-82-8) is a salt of two carnitine molecules with one tartaric acid, so a label mass for it counts the tartrate, and about 68 percent of that mass is L-carnitine. Only levocarnitine is the active ingredient of an FDA-approved drug, and the oral Carnitor label reports mild myasthenia only in uremic patients given DL-carnitine. Acetyl-L-carnitine sits separately in Category 1 of FDA's 503A compounding nominations list.
Many L-carnitine listings are ready-to-use liquids, and PeptideScouter computes a price per milligram only for vials labelled by mass. Liquid listings appear in the price table but on no per-milligram ranking, including liquids whose total content is recorded as a mass. The figure in a liquid's title is usually a concentration per milliliter and does not state what the vial holds. A few vendors sell vials labelled by total mass, and those listings do get a per-milligram figure.
Gut bacteria convert ingested L-carnitine to trimethylamine, which liver enzymes oxidize to TMAO. In Koeth and colleagues' 2013 Nature Medicine study, dietary L-carnitine increased TMAO and atherosclerosis in atherosclerosis-prone mice, but not when antibiotics suppressed the gut bacteria. In a cohort of 2,595 people undergoing cardiac evaluation, plasma L-carnitine predicted cardiovascular disease and events only among those with high TMAO, an observational association. The Carnitor labels list TMAO as a major metabolite of oral carnitine and note that TMA and TMAO may accumulate with chronic high oral doses in severe kidney impairment or on dialysis.
L-Carnitine is sold by 16 research peptide vendors indexed on PeptideScouter, with 20 tracked listings compared per vendor in the table above. Pricing is normalized and refreshed daily.
15 of the 16 indexed vendors currently have L-Carnitine in stock. The comparison table marks out-of-stock listings, and stock state is refreshed daily.
Northline Labs currently lists L-Carnitine at $0.06/mg, the lowest listed price across 16 tracked research peptide vendors. With current vendor discount codes applied, the lowest effective price is $0.05/mg.
Discount codes are issued per vendor rather than per peptide, so any code applies across that vendor's whole catalog. All 16 vendors listing L-Carnitine publish a PeptideScouter code, worth 10% to 20% off. Applied, the lowest effective price falls from $0.06/mg listed to $0.05/mg at Northline Labs. Each vendor's code is shown beside its price in the table above.
L-Carnitine ranges from $0.06/mg to $0.10/mg across 20 listings from 16 research peptide vendors, normalized to USD per milligram and refreshed daily.
16 research peptide vendors currently list L-Carnitine on PeptideScouter, with 15 in stock right now. We track 20 listings across size and kit variants.
L-Carnitine's CAS Registry Number is 541-15-1. It is also sold as L-Carnitine, Levocarnitine.
