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Mary Shomon

Thyroid Blood Tests: When to Take Thyroid Medication, Fasting, and More

By November 11, 2010

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A question I get asked regularly is whether or not doctors recommend that we take our thyroid medicine the day we are getting blood tests. And should we fast the night before thyroid tests? And does it matter whether we have tests in the morning, or in the afternoon? I've put together the answers in this piece on Optimum Time and Conditions for Thyroid Blood Tests. Also, learn about how TSH samples can degrade over time, in this article that talks about Capillary Fingerprick / Blood Spot Tests.

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Comments
November 12, 2010 at 9:37 am
(1) Kerry Finn says:

My doctor has me go for my TSH, free T3, and free T4 tests 24 hours after taking my medication.

November 12, 2010 at 6:14 pm
(2) Ed Arnold says:

I always get a blood-draw early in the morning, before taking my thyroid hormone. (I take synthetic T3 and T4.) I like to get the blood-draw before taking any T3 so I can better gauge how T4-T3 conversion is working. Doing the blood-draw before taking T3 shows me what my lowest FT3 is.

November 17, 2010 at 5:45 pm
(3) Ileen says:

The article didnt say when to OR not take your medication and then test?
What IS the right way.. My dr’s want to test with my NDT taken about 5or so hrs from dose taken..

what is the right way?

November 17, 2010 at 6:29 pm
(4) Monarch59 says:

I used to take mine (50 mcg Levothyroxine) in the a m. and my TSH was in the 2 area even though I felt super awful Now, that I take mine at bedtime, my TSH is in the 3 area and feeling 80% better. I could hardly walk becuz of feeling so weak and lethargic but yet the TSH showed I was feeling great.

In fact, the Middle Eastern doc, cut the dose to 25 mcg, I wanted to slap her. I begged for 3 yrs for her to increase it again becuz I had super dry eyes and a dry mouth. Her PA increased it and I thanked him a thousand times.

I Took it in the a m and had my blood work after school aroun 1 o’clock so that wasn’t good either.

Now, that I take the pill at bedtime, I feel this is a more true reading.

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