Bennydixie asked
I was thirteen weeks pregnant and diagnosed with an under active thyroid. I had a blood test on week ten and a repeat at 12 weeks. I have tsh level of 0.3. I was started on levothyroxine 50mg. After looking this up I see that biotin can effect readings. I’m taking a prenatal vitamin that contains this since week 9. I’m not sure should I stop taking prenatal vitamin or not. My next appointment with OB is three weeks. Can you give me advice?
Answer
Biotin, also known as Vitamin B7, is often present in prenatal vitamins to prevent deficiencies in vitamin B7 which can sometimes occur during pregnancy.
It is known that Biotin can affect some laboratory tests, including thyroid tests such as Thyroid Stimulating Hormone (TSH) and free thyroxine levels, resulting in falsely high or low levels depending upon the test used. In the case of TSH levels, taking Biotin can result in falsely lower reported TSH levels. This does not mean that the Biotin is adversely effecting your thyroid function, rather that Biotin is interfering with the thyroid lab test itself and causing false low levels to be reported.
So, What Should A Patient Do?
First, contact both your OBGYN and the doctor treating your reported low thyroid. The doctor that is treating your low thyroid, may want to repeat the lab work if he or she was not aware that the prenatal vitamin you are taking contains Biotin. Since Biotin is a water soluble vitamin, it is very quickly excreted from the body. Not taking the prenatal vitamin for 8 hours before the lab work may be enough to ensure accurate readings.
After having a discussion about the thyroid tests, you should then discuss with your OBGYN whether it is necessary to switch prenatal vitamins. Not all prenatal vitamins contain Biotin. However, it may be enough to just not take the prenatal before any thyroid lab work is done. This will be something that will need to be decided by your doctor(s). Below are a couple of examples of brands of prenatal vitamins that do not contain Biotin:
- OB Complete Premier
- OB Complete Petit
- R-Natal OB
- CitraNatal Harmony
Even though Biotin can interfere with certain lab tests, it is important not to just stop taking your prenatal vitamin without first consulting your doctor(s). Your doctor(s) may decide to switch your prenatal brand or have you not take the prenatal right before any thyroid testing. Either way, contacting your doctor(s) is necessary.
