What Causes Black Tarry Stools After Taking Methimazole?

Posted on Mon, 15 Sep 2014

Question: This week I was diagnosed with Graves' disease after blood work, low TSH, high T4, iodine uptake test with 29% at 6 hours and 50 something at 24 hours, and a thyroid scan. No thyroid swelling, no hot or cold nodules. Dr. did liver function and CBC before prescribing 10mg Methimazole 2x per day. I took 20 mg night before last, (per inst.), 10 mg yesterday morning and last night. This morning I have black tarry stools; however, i did eat a giant bowl of XXXXXXX as well as beets for lunch yesterday. I don't want to stop the medication - I really really want this to work as I am not a good candidate for RI yet because I am just now stopping smoking.

Answered by Dr. Binu Parameswaran Pillai (37 minutes later)

Brief Answer:
Hi

Detailed Answer:
Good day,
Noted your history.
The black tarry stools are unlikely to be due to the medications. However, we have to rule out very rare side effects of Methimazole and hence it is advisable to check CBC to look at your Hemoglobin and blood count. If the black tarry stools ( occasionally foul smell too), we need to rule out bleeding inside and hence it is recommended to do a stool test for blood.

Please remember that Grave;s disease only around 40 % of people respond to medicines and your chances of response may be better if you stop smoking and start taking Selenium 200 mcg supplements

Regards
Binu

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