When to measure Thyroxine level after taking drug

I have a approximately 10 year old male cocker spaniel who is taking
Thyroxine for a thyroid problem. The vet said he would measure the
thyroxine level 3 hours after the drug was taken. Is this the correct
time to do this? I have read on various internet resources that it
should be 4-6 hours.

The drug has been measured several times. The results are:

Canine total thyroxine(t4)
<9.99 nmol/litre
14.4 nmol/litre
24.1 nmol/litre.

What is the normal range for this?

"Polly Filler" <smudgepolly.TakeThisOut@hotmail.co.uk> wrote in message
news:57f328d7-3fdc-4a98-9895-a2483d0d71eb@r66g2000hsg.googlegroups.com...
> I have a approximately 10 year old male cocker spaniel who is taking
> Thyroxine for a thyroid problem. The vet said he would measure the
> thyroxine level 3 hours after the drug was taken. Is this the correct
> time to do this? I have read on various internet resources that it
> should be 4-6 hours.
>

Protocols may be different with different labs.

If they always measure 3 hours post pill then I'd imagine the results they
expect (and reference ranges) are going to be based on 3 hours post pill.
Anyone out there know the kinetics of thyroxine in a dog? (absorption rate
and half life specifically). These two numbers will tell you how sensitive
the timing of the test is. I've googled around a bit, but I'm finding
conflicting results.

Dale