How long is best to leave before blood test?

[lisan1]

18h or 30h? since last dose of levothyroxine?

[SeasideSusie Remembering]

If you can't leave 24 then go for 18 hours.

[lisan1 in reply to SeasideSusie]

Ok, thank you ever so much for your answer!

[PurpleDee]

I was diagnosed in October 2017; I had another blood test last month but I wasn't told to wait a certain amount of time after taking my levothyroxine. I took my dose about 7 am and had my test about 9 am. How long are you supposed to wait before having blood taken?

[SeasideSusie Remembering in reply to PurpleDee]

It's a patient to patient tip, although one member's endocrinologist has advised her to do exactly as we advise.

Leave 24 hours between last dose of Levo and blood draw.

Fast overnight (water allowed).

Book earliest appointment of the morning.

Most doctors dose by TSH only, ignoring how we feel and FT4/FT3. A lot of doctors think that once TSH is somewhere in range then everything is fine. The aim of a treated hypo patient generally is for TSH to be 1 or below or wherever it is needed for FT4 and FT3 to be in the upper part of their ranges. So if you are looking for an increase, or to avoid a reduction in dose, then we need TSH as high as possible. TSH is highest early in the morning and lowers throughout the day, also TSH lowers after eating, so an early blood draw after an overnight fast will give the highest TSH.

[PurpleDee in reply to SeasideSusie]

Thank you; I'm on 75mg but I think I may need to be on a higher dose, I've always been on average size 10/12 but in the last 18 months I've gone up to about 14/16 and I feel so bloated. Before I was diagnosed I was walking between 5 and 10 miles at the weekends but I was getting heavier. I have terrible brain fog, I can be in the middle of doing my work (mainly excel sheets) and I can literally in the blink of an eye forget what I'm doing. I keep having blanks when I'm having conversations. I thought this was all something to do with peri-menopause! My next blood test will be the end of April so I'll do what you've outlined. Thanks again.