L-carnitine side effects

Updated June 13, 2017

L-carnitine is also called levocarnitine and is used to prevent and treat a lack of this substance in the body. It's often associated with people who have kidney disease, who are on dialysis, or whose bodies can't properly assimilate carnitine from the diet. A lack of L-carnitine can lead to liver, heart and muscular problems.

Allergic Reactions

If you have ever had any unusual or allergic reaction to any other medications, tell your health care professional to prevent a potential allergic reaction to L-carnitine, warns the website People who have had allergic reactions to certain foods dyes, preservatives or animals may have an increased risk of an allergic reaction to L-carnitine.


Hypertension, or high blood pressure, occurs when the pressure required to pump blood through the arteries becomes too high and causes the heart muscle to work harder, effectively causing overload on the muscle. You may not experience any effects that you can feel from high blood pressure, but eventually it can cause heart damage, peripheral vascular damage and increase your risk of stroke and heart attack. One of the side effects of L-carnitine administration is high blood pressure, according to Your doctor should recommend consistent blood pressure monitoring while you take this drug.

Fast Heart Rate

This is also called tachycardia. A heart rate is considered abnormally high when it reaches over 100 beats per minute without an obvious reason, such as exercise, fear, anxiety, or fever, according to the US-based Heart Rhythm Society. Tachycardia is considered an arrhythmia that requires medical attention to prevent any significant side effects. Some people with tachycardia may feel no symptoms; others may experience shortness of breath, changes in vision, feeling faint, lightheadedness or chest discomfort. A fast heart rate or tachycardia is a side effect of L-carnitine, according to Your physician should ask you to report any instances in which you experience a fast heart rate for no apparent reason.


Experiencing a seizure from L-carnitine is a less common side effect than hypertension or fast heart rate, according to Seizures occur when the electrical stimulation in the brain is altered. You can see the effect of seizures when a person exhibits abnormal muscle movements, has visions or hallucinations or seems unable to respond to her environment. Seizures require medical attention and a change in the administration of L-carnitine.

Nausea, Vomiting, Cramps

If you experience a greater number of bowel movements than normal, you may be taking a higher dose of L-carnitine than needed. According to the University of Maryland Medical Center, diarrhoea is a side effect of L-carnitine when the person takes 5g or more of the supplement per day. Supplementation with L-carnitine can also cause other mild gastrointestinal symptoms such as nausea, vomiting and abdominal cramps, according to Linus Pauling Institute at Oregon State University.

Cite this Article A tool to create a citation to reference this article Cite this Article

About the Author

Gail Morris has been writing extensively since 1997. She completed a master's degree in nursing at Indiana University-Purdue University Indianapolis and practiced in medicine for more than 20 years. Morris has published medical articles in peer-reviewed journals and now writes for various online publications and freelances for Internet marketers.