L-Carnitine is often bought on impulse, "for fat loss" or "for energy", and almost never with any attention to how to actually take it. Yet dose, form and timing are what decide whether the supplement does anything measurable at all. Below is a practical, research-grounded breakdown: how much, when, and in what form.

How much: dosages from the research

The large majority of clinical studies used a range of 1–3 g of L-carnitine per day. That is the amount at which it makes sense to discuss any measurable effect on fatty-acid metabolism and recovery. Smaller doses (a few hundred milligrams) are mostly just topped into the body's own carnitine pool, which is not deficient in a healthy person.

  • General support: ~500 mg to 1 g/day.
  • Athletic context (performance, recovery): 2–3 g/day, split into 1–2 servings.
  • A single dose rarely exceeds 2 g, absorption does not scale proportionally beyond that; the excess is excreted.

The LC600 format is 600 mg per vial (lyophilisate), a convenient unit dose: one serving for support, two for the athletic range. Aim for the total daily amount rather than "one scoop".

When to take it

Less magic here than the marketing implies. What matters is consistency, because tissue carnitine accumulates gradually over weeks, not from a single dose.

  • Pre-workout (60–90 min before): the most popular schedule.
  • With a carbohydrate meal: the insulin response improves muscle carnitine retention, one of the few well-documented ways to raise its uptake.
  • Fasted uptake is lower; little point.

Forms: tartrate, acetyl, liquid or tablets

  • L-carnitine tartrate (LCLT): the common sports form, rapidly available, for performance and recovery.
  • Acetyl-L-carnitine (ALCAR): crosses into nervous tissue better; studied mainly in a cognitive context, not "fat burning".
  • Liquid vs tablets/powder: the difference is mostly convenience, not efficacy. Liquid is not "faster", that is marketing. A lyophilisate (like LC600) is a dry, reconstituted form with precise dosing and good stability.

How long to take it

Muscle-carnitine effects appear with sustained use (weeks to months), not acutely. Cycles are usually built in 8–12 week blocks. A "loading dose the day before competition" has no biological basis.

What not to combine it with, and cautions

  • High doses can cause GI discomfort and a characteristic fishy body odour (the metabolite trimethylamine), individually variable.
  • Discuss use with a physician if you have thyroid or kidney conditions, are pregnant, or take anticoagulants.
  • Carnitine is not a substitute for a caloric deficit: without one, do not expect an effect on body mass (see the separate weight-loss article).

In short

A working scheme for most people: 1–3 g/day, with a carbohydrate meal or pre-workout, over a multi-week cycle, form chosen by goal (LCLT for sport, ALCAR for cognition). Longeva LC600 material is supplied as a research-use-only reagent; every batch ships with purity data.