L-Carnitine L-Tartrate: What the Research Says

In short: L-carnitine L-tartrate (LCLT) is a common supplement form of carnitine, often sold for workout recovery. Small, mostly industry-linked studies suggest about 1–2 g a day may ease muscle soreness and some blood markers of muscle damage after hard training, but it hasn’t been shown to make people stronger, faster or leaner in a meaningful way. It’s usually well tolerated, though higher doses can cause stomach upset and a fishy body odor.

L-carnitine L-tartrate shows up in a lot of “recovery” and “fat burner” products. The pitch is simple: carnitine helps your body burn fat for energy, so taking more should help you recover faster, perform better and lose weight. The research is more modest than that. Here’s what the studies actually found, how much people took, and what to watch out for.

What is L-carnitine L-tartrate?

Carnitine is a compound your liver, kidneys and brain make from two amino acids, lysine and methionine. You also get it from food, mostly red meat: a 3-ounce beef steak has roughly 40–120 mg [1]. Healthy children and adults make enough on their own, so it isn’t considered an essential nutrient [1].

Its main job is to carry long-chain fatty acids into the mitochondria (the energy-making parts of your cells), where they’re burned for fuel [2]. That’s why it gets marketed for fat loss and endurance.

L-carnitine L-tartrate is simply carnitine bound to tartaric acid, a natural acid found in grapes. This “salt” form is a stable powder that’s easy to put in capsules and drinks. In a study in young pigs, LCLT was absorbed a bit faster than plain L-carnitine, but overall absorption was about the same [3]. So it isn’t a dramatically “better” form; it’s mainly a convenient one. You also absorb much less carnitine from supplements (about 14–18%) than from food (about 63–75%) [1].

Does it actually get into your muscles?

This is the big question, because about 95% of your body’s carnitine is stored in your heart and skeletal muscles [1]. Taking carnitine raises blood levels, but early studies found it didn’t raise muscle levels. In one study, 4 g a day for two weeks left muscle carnitine unchanged [4].

Later work showed it can be done, but slowly and with help from insulin. When 14 young men took 2 g of LCLT with 80 g of carbohydrate twice a day (about 640 extra calories a day from the sugary drink) for 24 weeks, muscle carnitine rose by 21% and work output in a cycling test improved by 11% compared with their starting point [5]. A similar 25-week study in 14 older men found a 20% rise in muscle carnitine and more fat burned during moderate exercise [6]. These are small studies with a demanding routine, so they show what’s possible, not what a typical scoop a day will do.

L-carnitine L-tartrate and muscle recovery

Recovery is where L-carnitine L-tartrate has its best evidence, though it comes mostly from one research group at the University of Connecticut, and several of its studies tested Lonza’s Carnipure product (Lonza makes L-carnitine).

• Less damage on scans. In a crossover study (where everyone tries both the supplement and a placebo) of 10 resistance-trained men, 2 g a day of carnitine as LCLT for three weeks lowered blood markers of muscle damage after a hard squat session. On MRI scans, the area of disrupted thigh muscle was about 41–45% of the placebo area [7].
• Hormones mostly unchanged. A follow-up in the same men found no direct effect on testosterone or growth hormone, only a rise in one growth-factor binding protein (IGFBP-3) [8].
• 1 g may be enough. In eight men, both 1 g and 2 g a day reduced markers of muscle damage and soreness after squats [9].
• Middle-aged adults too. In 18 men and women in their 40s and 50s, 2 g a day reduced soreness and damage markers, but strength and power didn’t change. This study named Carnipure as the product tested [10].

A 2020 meta-analysis (a study that pools results from several trials) of seven trials found that L-carnitine reduced muscle soreness for up to four days after exercise, and lowered blood markers of muscle damage at 24 hours, but not after that [11]. A 2024 umbrella review (a review of meta-analyses) rated the evidence for less soreness and lower creatine kinase (an enzyme that leaks from damaged muscle) as “moderate” certainty [12].

So L-carnitine L-tartrate may take a little of the edge off soreness after a tough session. What hasn’t been shown is that this turns into bigger gains over months of training. If recovery is your goal, the basics still matter more: enough sleep, enough protein spread over the day, and sensible training progressions (we cover protein timing in our post on the anabolic window).

Does it raise testosterone?

No good evidence says it does. In a three-week study of 10 trained men, LCLT increased the number of androgen receptors (the “docking sites” testosterone uses) in muscle before exercise, while testosterone levels themselves didn’t go up [13]. The researchers suggested this might help recovery, but nobody has shown it leads to more muscle. An older version of this article mentioned rat studies on testosterone and fertility; those were small animal studies in journals we couldn’t verify, so we’ve left them out.

Exercise performance: mixed results

A 2021 systematic review of 11 studies found that carnitine (including LCLT) sometimes improved high-intensity performance, for example more leg-press reps or higher sprint power, with 3–4 g taken 60–90 minutes before testing or about 2 g a day for 9–24 weeks. It found no benefit for moderate-intensity exercise like steady cycling or running [14].

Individual studies show how hit-and-miss this is. In 15 trained cyclists, 3 g of LCLT a day for four weeks didn’t change fat burning or 20 km time-trial performance [15]. An older version of this article quoted a “very recent” study saying 3 g of LCLT raised VO₂max (your maximum oxygen uptake) and running distance in wrestlers; it was published in a journal we couldn’t verify, so we’ve removed it.

The NIH Office of Dietary Supplements sums it up as “mixed” evidence for performance [1].

L-carnitine L-tartrate for weight loss

Carnitine is a common ingredient in fat burners. A 2020 meta-analysis of 37 trials found people taking L-carnitine lost about 1.2 kg (roughly 2.7 lb) more than those on placebo, mostly in people with overweight or obesity [16]. That’s a small difference, and most of these trials used plain L-carnitine, not LCLT specifically.

Not every trial agrees. In 36 women with overweight who walked four days a week, 4 g of L-carnitine a day for eight weeks made no difference to weight or body fat, and five women in the carnitine group dropped out because of nausea or diarrhea [17]. For more on how small most supplement effects on weight are, see our posts on L-carnitine and weight loss and hydroxycitric acid.

What about hair loss?

Researchers at the University of Hamburg found that LCLT helped hair follicles grow a little longer in lab dishes [18]. The same group later published a short report suggesting a topical LCLT lotion might help in people [19]. That’s early, lab-stage work. There are no good trials showing that taking LCLT by mouth helps with hair loss.

How much do studies use?

Most recovery studies used 1–2 g of carnitine a day, taken for about three weeks before testing [7, 9, 10]. Check the label: 2 g of L-carnitine L-tartrate supplies less than 2 g of actual carnitine, because part of the weight is the tartrate (roughly two-thirds is carnitine). The studies that raised muscle carnitine paired it with a large dose of carbohydrate and ran for about six months [5, 6]. For other forms of carnitine, see our posts on acetyl-L-carnitine and glycine propionyl-L-carnitine.

Side effects and safety

• Short-term safety looks good. In a small three-week study of 10 healthy men, 3 g a day of LCLT didn’t change blood counts or liver and kidney tests [20]. A 2006 risk assessment found strong evidence of safety up to 2 g of L-carnitine a day; its authors worked for a supplement-industry association, and there isn’t enough data on long-term use above that [21]. There’s no official upper limit [1].
• Common side effects. Around 3 g a day can cause nausea, vomiting, stomach cramps, diarrhea and a “fishy” body odor [1].
• The TMAO question. Gut bacteria turn unabsorbed carnitine into TMAO (trimethylamine N-oxide), which has been linked to heart disease. In mice, extra carnitine sped up hardening of the arteries, and in people, higher blood carnitine predicted heart problems only in those who also had high TMAO [22]. What this means for supplement users isn’t clear yet [1].
• Medications and conditions. Some anticonvulsants (especially valproic acid) and certain antibiotics lower carnitine levels, and carnitine has been linked to seizures in people with seizure disorders [1]. If you have kidney disease, a seizure disorder or heart disease, or take regular medication, check with your doctor first.

The bottom line on L-carnitine L-tartrate

L-carnitine L-tartrate isn’t a miracle fat burner or a testosterone booster. The most consistent finding is a modest drop in muscle soreness and damage markers after hard, high-rep training, mostly from small studies by one lab, often using the manufacturer’s product. Effects on strength, endurance and weight are small or inconsistent. If you want to try it, 1–2 g a day is the range studied, and it’s worth stopping if it upsets your stomach.

This article is for general information only and isn’t medical advice. Talk to your doctor or another qualified health professional before starting a new supplement. See our medical disclaimer.

References

1. NIH Office of Dietary Supplements. Carnitine: Fact Sheet for Health Professionals. Updated April 17, 2023. ods.od.nih.gov
2. Kerner J, Hoppel C. Fatty acid import into mitochondria. Biochim Biophys Acta. 2000;1486(1):1-17. doi:10.1016/s1388-1981(00)00044-5
3. Eder K, Felgner J, Becker K, Kluge H. Free and total carnitine concentrations in pig plasma after oral ingestion of various L-carnitine compounds. Int J Vitam Nutr Res. 2005;75(1):3-9. doi:10.1024/0300-9831.75.1.3
4. Barnett C, Costill DL, Vukovich MD, et al. Effect of L-carnitine supplementation on muscle and blood carnitine content and lactate accumulation during high-intensity sprint cycling. Int J Sport Nutr. 1994;4(3):280-288. doi:10.1123/ijsn.4.3.280
5. Wall BT, Stephens FB, Constantin-Teodosiu D, et al. Chronic oral ingestion of L-carnitine and carbohydrate increases muscle carnitine content and alters muscle fuel metabolism during exercise in humans. J Physiol. 2011;589(4):963-973. doi:10.1113/jphysiol.2010.201343
6. Chee C, Shannon CE, Burns A, et al. Increasing skeletal muscle carnitine content in older individuals increases whole-body fat oxidation during moderate-intensity exercise. Aging Cell. 2021;20(2):e13303. doi:10.1111/acel.13303
7. Volek JS, Kraemer WJ, Rubin MR, et al. L-Carnitine L-tartrate supplementation favorably affects markers of recovery from exercise stress. Am J Physiol Endocrinol Metab. 2002;282(2):E474-E482. doi:10.1152/ajpendo.00277.2001
8. Kraemer WJ, Volek JS, French DN, et al. The effects of L-carnitine L-tartrate supplementation on hormonal responses to resistance exercise and recovery. J Strength Cond Res. 2003;17(3):455-462. PubMed 12930169
9. Spiering BA, Kraemer WJ, Vingren JL, et al. Responses of criterion variables to different supplemental doses of L-carnitine L-tartrate. J Strength Cond Res. 2007;21(1):259-264. doi:10.1519/00124278-200702000-00046
10. Ho JY, Kraemer WJ, Volek JS, et al. L-Carnitine L-tartrate supplementation favorably affects biochemical markers of recovery from physical exertion in middle-aged men and women. Metabolism. 2010;59(8):1190-1199. doi:10.1016/j.metabol.2009.11.012
11. Yarizadh H, Shab-Bidar S, Zamani B, et al. The effect of L-carnitine supplementation on exercise-induced muscle damage: a systematic review and meta-analysis of randomized clinical trials. J Am Coll Nutr. 2020;39(5):457-468. doi:10.1080/07315724.2019.1661804
12. Talebi S, Mohammadi H, Zeraattalab-Motlagh S, et al. Nutritional interventions for exercise-induced muscle damage: an umbrella review of systematic reviews and meta-analyses of randomized trials. Nutr Rev. 2024;82(5):639-653. doi:10.1093/nutrit/nuad078
13. Kraemer WJ, Spiering BA, Volek JS, et al. Androgenic responses to resistance exercise: effects of feeding and L-carnitine. Med Sci Sports Exerc. 2006;38(7):1288-1296. doi:10.1249/01.mss.0000227314.85728.35
14. Mielgo-Ayuso J, Pietrantonio L, Viribay A, et al. Effect of acute and chronic oral L-carnitine supplementation on exercise performance based on the exercise intensity: a systematic review. Nutrients. 2021;13(12):4359. doi:10.3390/nu13124359
15. Broad EM, Maughan RJ, Galloway SD. Effects of four weeks L-carnitine L-tartrate ingestion on substrate utilization during prolonged exercise. Int J Sport Nutr Exerc Metab. 2005;15(6):665-679. doi:10.1123/ijsnem.15.6.665
16. Talenezhad N, Mohammadi M, Ramezani-Jolfaie N, et al. Effects of L-carnitine supplementation on weight loss and body composition: a systematic review and meta-analysis of 37 randomized controlled clinical trials with dose-response analysis. Clin Nutr ESPEN. 2020;37:9-23. doi:10.1016/j.clnesp.2020.03.008
17. Villani RG, Gannon J, Self M, Rich PA. L-Carnitine supplementation combined with aerobic training does not promote weight loss in moderately obese women. Int J Sport Nutr Exerc Metab. 2000;10(2):199-207. doi:10.1123/ijsnem.10.2.199
18. Foitzik K, Hoting E, Förster T, Pertile P, Paus R. L-carnitine-L-tartrate promotes human hair growth in vitro. Exp Dermatol. 2007;16(11):936-945. doi:10.1111/j.1600-0625.2007.00611.x
19. Foitzik K, et al. Indications that topical L-carnitin-L-tartrate promotes human hair growth in vivo. J Dermatol Sci. 2007;48:141-144. doi:10.1016/j.jdermsci.2007.07.001
20. Rubin MR, Volek JS, Gómez AL, et al. Safety measures of L-carnitine L-tartrate supplementation in healthy men. J Strength Cond Res. 2001;15(4):486-490. PubMed 11726261
21. Hathcock JN, Shao A. Risk assessment for carnitine. Regul Toxicol Pharmacol. 2006;46(1):23-28. doi:10.1016/j.yrtph.2006.06.007
22. Koeth RA, Wang Z, Levison BS, et al. Intestinal microbiota metabolism of L-carnitine, a nutrient in red meat, promotes atherosclerosis. Nat Med. 2013;19(5):576-585. doi:10.1038/nm.3145