Does b12 affect thyroid test?

If you are short on time, just schedule your thyroid test in the morning on an empty stomach. B12 does not interfere with TSH levels directly. Just make sure you inform the lab technician about any supplements you are taking so they can note it down.

I am a bit new to all this and just got my first thyroid prescription. I also take a daily B12 capsule because I don't eat meat. Do you think I should ask the lab about this before my blood draw next week, or is it okay to just go?

I used to ignore my fatigue thinking it was just a minor B12 issue, but it turned out to be severe hypothyroidism. Please get both B12 and thyroid panels done properly at a lab. Don't worry about the supplement affecting the test, just go get checked before your symptoms get worse like mine did.

You do not need to worry about this. B12 is safe and generally does not interfere with your thyroid blood tests. Just follow your doctor's instructions for the test day, and I hope your reports come back normal.

Don't worry, standard B12 supplements do not alter your thyroid test results. I have been taking thyroid medication and B12 for years and my doctor always tests them together. Just keep a gap of a few hours between your thyroid pill and other vitamins.

My endocrinologist clarified that B12 itself has no impact on T3, T4, or TSH assays. However, many B12 supplements contain Biotin (Vitamin B7) which can cause falsely high or low thyroid results depending on the lab method. He advised stopping any biotin-containing supplements 48 hours prior to testing.