What Causes Rapid Heart Rate And Headache While On Levothyroxine?

Posted on Thu, 19 Nov 2015

Question: I have been hypothyroid for many years but a recent TSH test showed I am below the therapeutic level. I had a Free T-4 test done and I was within therapeutic level for that. I've been on levothyroxine at 137 mcg for probably 15 yrs. Because I had a rapid heart beat (130 to 140 BPM) and was getting lots of headaches I reduced my thyroid pill to taking it every day and feel much better. I did leave a message with my dr's nurse about this reduction and they did order the Free T-4 test which I had done on Wednesday. My question is do I have hyperthyroidism since the Free T-4 test was normal?

Answered by Dr. Ajish TP (44 minutes later)

Brief Answer:
Hypothyroidism

Detailed Answer:
Hi,

Welcome to HCM. I have gone through your question and understand your concerns.

Levothyroxine is given for HYPOTHYROIDISM. You are having under-active thyroid. Once on treatment with levothyroxine, the free T4 has to be in therapeutic range or near the upper limit of therapeutic level.

While on treatment with levothyroxine, you may experience rapid heart beat and headaches. The treatment of this is to reduce the levothyroxine dose and retesting after 6 weeks. If TSH goes above therapeutic level, the dose has to be increased back. If rapid heart rate and headache persists, some dugs like betablockers can be tried.

Hope I have answered your question. If you have ant further questions I will be happy to help you.

Regards,
Dr Ajish TP
Consultant Endocrinologist

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Above answer was peer-reviewed by : Dr. Chakravarthy Mazumdar