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Acetyl-L-carnitine

Supplement amino acid derivative brain & moodenergy
Aka: ALCAR, acetylcarnitine
Brands seen in Singapore: California Gold Nutrition, NOW Foods, Nutricost, MRM Nutrition, Thorne
Third-party tested: Thorne certifies other products with NSF Certified for Sport, but nothing for acetyl-l-carnitine.Certification is granted per product, so check the tub you actually own. Not being listed is not the same as failing.
Not medical advice. Check with your doctor or pharmacist before you start, stop or change the timing of anything you take.
How to use
What it’s for
Mixed results in dementia trials; gains faded by 52 weeks
Pros & cons
Pros
  • Trials used 1.5–3 g a day for 3–12 months
  • A 2003 meta-analysis of 21 trials scored better
  • Carnitine carries fatty acids into mitochondria
Cons
  • A Cochrane review saw no benefit held at 52 weeks
  • ~3 g/day can bring nausea, cramps, fishy body odour
  • Gut bacteria turn carnitine into TMAO, tied to CVD risk
Sources
  1. NIH ODS — Carnitine, Fact Sheet for Health Professionals (read via archive.org; ods.od.nih.gov returned 403) · read 2026-08-27
    what it says
    “Carnitine does not have an established tolerable upper intake level. However, doses of approximately 3 g/day of carnitine supplements can cause nausea, vomiting, abdominal cramps, diarrhea, and a fishy body odor”
  2. NIH ODS — Dietary Supplements for Weight Loss (Health Professional) · read 2026-08-27
    what it says
    “Carnitine supplements are well tolerated and generally safe at doses up to about 4 g/day, although they can cause nausea, vomiting, abdominal cramps, diarrhea, and a fishy body odor”
  3. HSA — Guidelines on Prohibited and Restricted Ingredients in Health Supplements and Traditional Medicines (Oct 2025), Annex A · read 2026-08-27
    what it says
    “A list of specific prohibited and restricted ingredients is provided in Annex A … This list is not exhaustive. Dealers are responsible to ensure that their products are safe and appropriate for the target consumers.”
  4. HSA — Health Supplements Guidelines (Jan 2026), Tables 4–5 · read 2026-08-27
    what it says
    “HS for use by the general adult population should not contain vitamins and minerals exceeding the stipulated limits stated in Tables 4 and 5.”
  5. iHerb Singapore — Acetyl L-Carnitine category page (Supplements > Amino Acids), default order · read 2026-08-27
    what it says
    “California Gold Nutrition, Acetyl-L-Carnitine, 500 mg, 60 Veggie Capsules … NOW Foods, Acetyl-L-Carnitine, 500 mg, 100 Veg Capsules”
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Updated 2026-08-30. Every line above traces to a numbered source. Kozen-X is not a medical device and does not give medical advice. It lists what published sources have written down — nothing more. A pair not listed is unrecorded, not cleared. Before you start, stop or re-time anything, talk to your doctor or pharmacist.