L-Carnitine
Amino Acid Derivative · Fatty Acid Transporter
L-Carnitine is an amino acid derivative naturally produced in the body and essential for transporting long-chain fatty acids into mitochondria for energy production. Injectable forms bypass digestive absorption limitations of oral supplements.
Overview
L-Carnitine is an amino acid derivative naturally produced in the body and essential for transporting long-chain fatty acids into mitochondria for energy production. Injectable forms bypass digestive absorption limitations of oral supplements.
Acts as a carrier molecule, shuttling long-chain fatty acids across the inner mitochondrial membrane via the carnitine palmitoyltransferase (CPT) system. This is the rate-limiting step in fatty acid oxidation for energy production.
Research indications
What the compound has been studied for, grouped by body system. Effect size is the reported magnitude where it was measured — not a recommendation.
Primary function transporting fatty acids into mitochondria for beta-oxidation.
Supports ATP generation from fat metabolism, particularly during exercise.
May enhance fat utilization when combined with exercise and caloric deficit.
May reduce muscle damage markers and improve recovery post-exercise.
Enhances fat utilization during prolonged exercise, potentially sparing glycogen.
FDA-approved treatment for primary and secondary carnitine deficiency.
Used in patients on hemodialysis who develop carnitine depletion.
A large effect in a weak study and a small effect in a strong one are different things. Effect size is never evidence of use in people.
- Class
- Quaternary ammonium compound
- Molecular weight
- 161.2 Da
- Half-life
- ~2.5 h
- Typical dose
- 50-200mg daily
- Frequency
- Once daily or pre-workout
- Cycle length
- 8-16 weeks (can be used continuously)
- Storage
- Lyophilized: -20°C; Reconstituted: 2-8°C for 2-4 weeks
Molecular data
- Type
- Quaternary ammonium compound
- Molecular weight
- 161.2 Da
- Half-life
- 150 min
Dosing reference
Doses reported in the literature and by suppliers. These are a record of what has been used in research — reference, never instruction.
| Context | Route | Amount | Frequency |
|---|---|---|---|
| Standard Protocol | SubQ | 50-100mg | Daily |
| Advanced Protocol | SubQ or IM | 100-200mg | Daily |
| Pre-Workout | SubQ | 100-200mg | 30-60 min before exercise |
Interactions
L-Carnitine may affect thyroid hormone action. Those on thyroid medication should monitor levels.
May enhance effects of warfarin and similar medications.
Quality checklist
- ✓White crystalline powder
- ✓Clear, colorless solution after reconstitution
- ✓Certificate of Analysis with purity testing
- !Should dissolve completely without residue
- ×Discolored powder
- ×Cloudy or particulate solution
- ×Strong unusual odor
What to expect
Safety
- Injection site reactions
- Mild nausea
- Body odor (fishy smell at high doses)
- Allergic reactions (rare)
- Severe gastrointestinal distress
- Unusual muscle weakness
- Seizure disorders (may lower seizure threshold)
- Hypothyroidism (may affect thyroid function)
- Allergy to carnitine products
FAQ
Why inject L-carnitine when oral supplements are available?
Oral L-carnitine has only 15-20% bioavailability due to poor intestinal absorption. Injectable forms achieve near 100% bioavailability, delivering much higher effective doses directly into circulation. Injectable is significantly more efficient if cost and needle anxiety aren't factors.
Does L-carnitine actually help fat loss?
L-carnitine enhances fatty acid transport into mitochondria for energy production. It works best when combined with exercise and caloric deficit. Modest benefits (5-10% improvements in fat loss) are most visible in well-trained athletes or those with pre-existing carnitine deficiency.
Can I take L-carnitine before cardio?
Yes. Injecting 100-200mg 30-60 minutes before endurance exercise optimizes fatty acid utilization and may improve performance slightly. Time it to maximize fat-burning potential, though benefits are most apparent during prolonged low-to-moderate intensity work.
Will L-carnitine affect thyroid function?
L-carnitine may affect thyroid hormone action in some individuals. If you're on thyroid medication (T3/T4), monitor thyroid levels before and after starting carnitine supplementation. Adjustments to thyroid dosing may be necessary in some cases.