- Trouble sleeping
- Increased heart rate
- Nausea
- Vomiting
- Fever
- Increased blood pressure
It's possible that you could experience some of these side effects, though most people will be fine when taking L-carnitine in recommended daily amounts. The amount of L-carnitine that you should take is between 500 and 1,000 mg. This amount can be taken up to 3 times per day. The total per day would be 3,000 mg.
If you have ever had a seizure, you should not take L-carnitine because it could possibly cause you to have another seizure.
If you have been diagnosed with hypothyroidism, L-carnitine could worsen your condition. It would be best if you didn't take this supplement.
If you are pregnant or nursing, not enough is known about L-carnitine supplements and pregnancy. You should stay on the safe side and avoid use of this supplement while pregnant or nursing. Small amounts found in food are just fine though.