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The 5 Best Carnitine Supplements

Why should you consider carnitine?

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The amino acid called carnitine isn’t technically essential, but many have found reasons to add it to their supplement regimen. It’s possible that it may have applications for exercise performance and longevity, bit how do you decide which product to buy? We’ve looked at the top products on the market to bring you these excellent options.

L-carnitine Featured Image

Best Overall

Added Calcium

The very name Optimum Nutrition will bring comfort to many consumers. The makers of the most popular protein powder on the market, Optimum Nutrition is renowned for their quality control and their value — plus, these are tablets, not capsules, so they’re vegan friendly.


  • Due to the company’s size and economy of scale, Optimum Nutrition makes pretty reasonably priced supplements.
  • Each tablet provides 500 milligrams of l-carnitine tartrate.
  • The tablets include 10 percent of the recommended intake of calcium.


  • The ingredients list includes silica, pharmaceutical glaze, stearic acid, and the disintegrant croscarmellose sodium. If you’re looking for a product that’s pure carnitine, it’s not this.
Optimum Nutrition L-Carnitine 500mg Tablets
Optimum Nutrition L-Carnitine 500mg Tablets
Optimum Nutrition L-Carnitine 500mg Tablets

These carnitine tablets are easy to ingest, rigorously tested, and have added calcium.

Runner Up

Best for the Brain?

Acetyl L-Carnitine may cross the blood brain barrier more effectively than l-carnitine, and Nutricost provides some of the best supplements on the market. A big standout is that the product is third party tested, plus one little tub provides a considerable 500 servings of one gram each.


  • All of Nutricost’s products are third party tested.
  • This is pure carnitine: absolutely no other ingredients are included.


  • With 500 servings, some customers have noted the product can expire before they finish the tub.
  • Pure carnitine can have a strong sour taste.
Nutricost Acetyl L-Carnitine (ALCAR) 500 Grams
Nutricost Acetyl L-Carnitine (ALCAR) 500 Grams
Nutricost Acetyl L-Carnitine (ALCAR) 500 Grams

This carnitine is third party tested and has no extra ingredients at all.

Best for Athletes

No Banned Substances

NOW Sports offers one of the few carnitine supplements to be not only certified by Informed Choice — meaning the facilities are inspected for banned substances — but also Informed Sport, which means each batch of the product is tested. Many athletes only take products with these certifications, plus it comes in an unusual, Tropical Punch-flavored liquid form.


  • The product has been rigorously tested for banned substances and performance enhancers.
  • It includes a dose of Vitamin B6, which may contribute to muscle retention.
  • Carnitine is often maligned for its sour taste, but NOW Sports has naturally flavored their beverage so it goes down easily.


  • With all the testing and the flavoring, this winds up as one of the pricier ways to ingest carnitine.
NOW Sports L-Carnitine Liquid 1000 mg
NOW Sports L-Carnitine Liquid 1000 mg
NOW Sports L-Carnitine Liquid 1000 mg

One of the few carnitine supplements certified buy Informed Sport.

Best Capsules

3 Types of Carnitine

If you’re not after funky tasting powder, sweetened liquid, or filler-filled tablets, Life Extension makes a solid capsule that’s made from vegetable cellulose, so it’s free from animal products. In addition to using very few ingredients and providing 1.4 grams of carnitine per serving, it’s made in an NSF registered facility, so it’s audited for quality and purity.


  • The product includes three kinds of carnitine.
  • The capsules are vegetarian friendly.
  • Life Extension’s facility is NSF certified.


  • This isn’t the cheapest carnitine on the market.
  • The capsules contain silica, which some prefer to avoid.
Life Extension Optimized Carnitine
Life Extension Optimized Carnitine
Life Extension Optimized Carnitine

Three types of NSF-certified carnitine that's encased in vegetarian capsules.

Best for Buying in Bulk

Lab Tested and Unflavored

Buy bulk, save cash, at least if you’re really taking a lot of carnitine. BulkSupplements is indeed the best way to buy up to a thousand servings of carnitine at once, and the quality is superb: it contains absolutely nothing but acetyl l-carnitine, it’s tested both in house and by a third party to ensure quality, and it’s made in a facility free from major allergens.


  • BulkSupplements offers the opportunity to buy large amounts of product to save on cost per serving.
  • The product is tested in house and by a third party for purity.
  • There are no added ingredients whatsoever.


  • Some find the bag doesn’t always seal very well.
  • Pure carnitine has a pretty sour taste that not everyone’s a fan of.
BulkSupplements.com ALCAR HCl
BulkSupplements.com ALCAR HCl
BulkSupplements.com ALCAR HCl

Pure acetyl l-carnitine that's unflavored and lab tested for purity.

What Are the Benefits of Carnitine?

There are several reasons people might be interested in this supplement.

  • Longevity

Carnitine seems to help your mitochondria function and produce energy, and supplementing may improve mitochondrial function, which plays a role in immunity and longevity.(1)(2)

  • Fat Loss

Carnitine seems to help move more fatty acids into your cells to be used for energy, so there’s a popular theory that it can be useful as a weight loss supplement. Human studies are mixed, though — some analyses saw significant weight loss, particularly among obese or older adults, while others saw none.(3)(4) More research is needed, particularly in young subjects.

  • Better Muscle

Carnitine, particularly the form called L-Carnitine L-Tartrate, may help to reduce muscle damage experienced during exercise.(5)(6)(7) This research used doses of two grams per day. There’s also research suggesting that carnitine helps build and retain lean muscle among the elderly, but there’s not a lot of evidence on young, healthy folks.(8)(9)

  • Better Cardio Workouts

Two to four grams of carnitine per day has seen an increase in anerobic output, meaning short bouts of high intensity exercise.(10)(11)

  • Sperm Quality

High doses of carnitine — two or three grams daily —     appears to increase sperm quality with regards to sperm morphology.(12)

BarBend Tips

  • There are several forms of carnitine. L-carnitine is typical, but among others there’s also d-carnitine (which seems to limit your absorption of more usable carnitine, so it may be best to avoid), l-carnitine l-tartrate (perhaps most common in sports supplements as it absorbs quickly) and acetyl-L-carnitine, which is almost identical to regular carnitine but it’s been acetylated, so it may cross the blood-brain barrier more efficiently.(13)(14)(15)
  • The best dietary source of carnitine is meat and in particular beef, which provides 56 to 162 milligrams of carnitine per 4-ounce serving.
  • A pretty typical dosage is 250 to 500 milligrams twice per day, though a lot of the research mentioned above used two to three grams a day. It’s usually recommended to start with a lower dose and work your way up.
  • For your body to produce plenty of its own carnitine, it appears to be important to eat plenty of Vitamin C.(16)

Wrapping Up

Carnitine comes in many forms and can serve many purposes, but it’s of the utmost importance that you speak with a physician before making any additions to your nutrition and supplement regimen.


1. Iossa, S et al. Acetyl-L-carnitine Supplementation Differently Influences Nutrient Partitioning, Serum Leptin Concentration and Skeletal Muscle Mitochondrial Respiration in Young and Old Rats. J Nutr . 2002 Apr;132(4):636-42.
2. Rosca, M et al. Mitochondria in the Elderly: Is Acetylcarnitine a Rejuvenator? Adv Drug Deliv Rev . 2009 Nov 30;61(14):1332-1342.
3. Pooyandjoo, M et al. The Effect of (L-)carnitine on Weight Loss in Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. Obes Rev . 2016 Oct;17(10):970-6.
4. Broad, E et al. Effects of Four Weeks L-carnitine L-tartrate Ingestion on Substrate Utilization During Prolonged Exercise. Int J Sport Nutr Exerc Metab . 2005 Dec;15(6):665-79.
5. Kraemer, W et al. The Effects of L-carnitine L-tartrate Supplementation on Hormonal Responses to Resistance Exercise and Recovery. J Strength Cond Res . 2003 Aug;17(3):455-62.
6. Spiering, B et al. Effects of L-carnitine L-tartrate Supplementation on Muscle Oxygenation Responses to Resistance Exercise. J Strength Cond Res . 2008 Jul;22(4):1130-5.
7. Volek, J et al. L-Carnitine L-tartrate Supplementation Favorably Affects Markers of Recovery From Exercise Stress. Am J Physiol Endocrinol Metab . 2002 Feb;282(2):E474-82.
8. Malaguarnera, M et al. L-Carnitine Treatment Reduces Severity of Physical and Mental Fatigue and Increases Cognitive Functions in Centenarians: A Randomized and Controlled Clinical Trial. Am J Clin Nutr . 2007 Dec;86(6):1738-44.
9. Pistone, G et al. Levocarnitine Administration in Elderly Subjects With Rapid Muscle Fatigue: Effect on Body Composition, Lipid Profile and Fatigue. Drugs Aging . 2003;20(10):761-7.
10. Jacobs, P et al. Glycine propionyl-L-carnitine Produces Enhanced Anaerobic Work Capacity With Reduced Lactate Accumulation in Resistance Trained Males. J Int Soc Sports Nutr . 2009 Apr 2;6:9.
11. Wall, B 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 Feb 15;589(Pt 4):963-73.
12. Lenzi, A et al. Use of Carnitine Therapy in Selected Cases of Male Factor Infertility: A Double-Blind Crossover Trial. Fertil Steril . 2003 Feb;79(2):292-300.
13. Spasov, A et al. Effects of L-, D-, and DL-carnitine on Morphometric Parameters of Skeletal Muscle and Exercise Performance of Laboratory Animals Receiving Carnitine-Deficient Diet. Bull Exp Biol Med . 2006 Oct;142(4):458-60.
14. Traina, G. The Neurobiology of acetyl-L-carnitine. Front Biosci (Landmark Ed) . 2016 Jun 1;21:1314-29.
15. Trappe, S et al. The Effects of L-carnitine Supplementation on Performance During Interval Swimming. Int J Sports Med . 1994 May;15(4):181-5.
16. Steiber, S et al. Carnitine: A Nutritional, Biosynthetic, and Functional Perspective. Mol Aspects Med . Oct-Dec 2004;25(5-6):455-73.

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