Second set of blood tests coming up.

[Jukebox1]

I was diagnosed underactive thyroid in June, also suspected diabetes type 2 (nurse advised I could reverse with weight loss and exercise, and I have lost a stone) I am due for repeat blood tests now and wonder why people are being advised not to take their levothyroxine before the tests. Thank you.

[shaws Administrator]

Because if you have just digested levo a few hours beforehand, it skews the results completely and you may end up with the GP (as they only take notice of the blood test which they shouldn't do) reducing or keeping you on the same dose when in fact you may really need an increase.

[Clutter]

Jukebox, Levothyroxine peaks in the blood 2-6 hours after ingestion so taking it before your blood test means you are getting a measurement of the peak levels rather than the normal circulating levels. As Shaws said, this can mean that some doctors will reduce a patient's dose or fail to agree an increase which may be needed to resolve symptoms and effectively leaves a patient under medicated.