Pre Blood test

[Print1972]

Hi. I've noticed that many people fast before their blood test and also wait to take Levo, until afterwards. My GP has never given this advice. I was diagnosed 5 months ago and have had two blood tests since. Next one due in 4 weeks. Does everyone advise fasting and waiting to take Levo?

[greygoose]

If they're thyroid bloods, yes. The point is that the TSH is highest first thing in the morning, and drops throughout the day. It also drops after eating. As all most doctors really look at is the TSH, most people want it as high as possible, either to get a diagnosis, or to get an increase in dose, or to not have a reduction in dose.

If you take your levo before the blood draw, all you will be measuring, if they do the FT4, is the dose you just took, not the normal level of circulating hormone. (It might also affect the TSH, but that's not proven.) So, if your doctor tests the FT4, you do not want the level way over-range, as it would be if you took your levo just before. 24 hours should be left between the last dose and the blood draw.

But doctors don't seem to realise any of that. If you ask them, they will say it doesn't make any difference. Whereas we have proof positive that it does!

[shaws Administrator]

Doctors are unaware of anything, really, to do with hypothyroidism. It is us, the patients, who have sussed the best way to get the best results from our blood tests.

For instance doctors seem to look only at the TSH (thyroid stimulating hormone - which is from the pituitary gland).

TSH drops throughout 24 hours of the day, so if you got your blood test at 4 p.m. it will be different than at 9 a.m. and if you've just taken your dose of levo a couple of hours before it will probably reduce the TSH too low and T4 high and the doctor will promptly reduce your dose of levo to bring both within the range. whereas we feel best with a TSH of around 1 or lower.

GPs don't seem to understand that TSH isn't a thyroid hormone and adjusting doses of levo makes us unwell if the dose of levo is reduced which is a thyroid hormone.

The forum's advice is fast and take levo afterwards (or any other thyroid hormone one takes). It gives the patient an advantage.

[cjrsquared]

There is debate about whether to take medication or not, but grey goose is correct about TSH being highest in the morning and falling after eating. What you want is to compare blood results over time to see if any dose change is making a difference. Therefore you want bloods taken at comparable times of day with the similar length of time since medication and eating. It is easier to fast (except water) and delay dose rather than other variables. Remember that ft4 rises and peaks 4-6 hours after levothyroxine. Hope this helps.

[Print1972]

Thanks everyone. I'll take your advice and hopefully my results will be more accurate.