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Question:
A few weeks after starting acetyl-L-carnitine, I became so sluggish I could hardly function. Could this be due to the supplement?

Answer:
Research has shown that carnitine can potentially impair the action of thyroid hormone -- which can cause fatigue and weakness. While this would not be expected to affect people with normal thyroid function, if you have low or borderline-low thyroid levels, this may explain your symptoms. Use of acetyl-L-carnitine or other forms of carnitine is not advisable when thyroid levels are low -- a condition particularly common among women older than 60 years. This and several other potential side effects of acetyl-L-carnitine are described in the "Concerns and Cautions" section of ConsumerLab.com's Acetyl-L-Carnitine Supplements Review >>

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Sara15535   September 14, 2017
What about L-Theanine? Is there any contradiction with it and thyroid meds?

ConsumerLab.com   September 25, 2017
Hi Sara - We aren't aware of any studies on the effects of L-theanine on thyroid function or interactions with thyroid medication.

This CL Answer initially posted on 4/19/2013. Last updated 8/8/2017.

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