Blood test timing

[Tanyaking]

I know for a blood test I’m to leave 8-12 hours without anything with T 3 in it ..but my natrapath has said this is measuring the ..trough.. of what’s happening and I need too have bloods after 5 hours which will measure the plasma peak and will be the true numbers of what is going on regarding dose and bloods ...Does that sound about right?

[helvella Administrator Thyroid UK]

Why is a peak - which lasts for a relatively short period - more relevant than the trough which lasts, depending on exact definition, for hours?

Why five hours?

A 2016 paper shows some graphs of T3 levels in people under experimental T3 treatment.

ncbi.nlm.nih.gov/pmc/articl...

See figure 3.

ncbi.nlm.nih.gov/pmc/articl...

It shows T3 and FT3 peaking two hours after administration. Then falling steadily for about six hours. (We are left to assume it continues that downward path but at a slower and slower rate until the next dose. The graph only covers eight hours.)

Five hours would be an arbitrary three hours into the downward slope. Why then? Why not at peak?

Of course, trying to get that peak requires you to have your blood taken in a small time window, I suggest less than one hour, based on two hours after your tablet.

How many of us can get blood draw appointments that precise?

(That paper shows TSH levels across the entire study being from slightly under 2 to 6. With it starting around 2 and ending around 4. That is near-certain proof of under-dosing.

ncbi.nlm.nih.gov/pmc/articl... )

I'd argue that the peak is almost entirely the effect of the ingested T3 and says next to nothing about what your body is doing with it.

What would be interesting is to see hourly TT3 and FT3 levels across 24 hours. But that isn't remotely feasible.

[greygoose]

Naturopaths have some very strange ideas about thyroid and how to treat them.

[SlowDragon Administrator]

Would be suspicious that measuring peak is an excuse for then reducing dose

[shaws Administrator]

Our head can spin when trying to figure out what is best for us to recover and then 'experts' come along and confuse the issue altogether, I feel.

What we, the patient, needs is a TSH. FT4 and FT3 - the latter rarely tested.

thyroiduk.org.uk/tuk/testin...