Read about L-Carnitine benefits and more.

L-Carnitine side effects

Prior to taking L-Carnitine supplements or items that contain added amounts of it, you should consider potential side effects, as well as other issues, such as interactions with other supplements, medications, or herbal medicines. Additionally, it may be contraindicated in certain individuals or those with particular conditions. This page regarding side effects and other precautions is not intended to be an exhaustive list, and it does not cover all potential issues. Find professional / qualified assistance when determining whether to take L-Carnitine and what its potential precautions are.

Side Effects

Ingesting normal amounts of L-Carnitine does not typically lead to serious side effects. If it leads to extra energy, the individual may have difficulty falling asleep if taking the supplement in the evening (or prior to sleeping).

Some of the mild or moderate potential side effects that have been reported are: restlessness, headache, diarrhea, nausea, vomiting, decreased appetite, and stuffed nose. A fever, rise in blood pressure, or quickened heart rate can be a serious side effect. The potential decreased appetite can also lead to an eating disorder, such as anorexia nervosa.


For individuals with underactive thyroid function, or one which is borderline, L-Carnitine should not be taken. It may damage the function of the already low levels of thyroid hormones. L-Carnitine intake is also contraindicated for individuals on dialysis.


It is possible for L-Carnitine to interact with some medications, herbs, and/or other supplements. Several medicines with which this is a possibility are AZT, doxorubicin, isotretinoin, and valproic acid. Before beginning to use this supplement, find out about other potential interactions and consider any items that you may be taking. Look for qualified advice on whether L-Carnitine might interact with the particular supplements, herbal medicines, or drugs that you may be using.