What’s the fasting protocol for a thyroid test for my dog?
October 28, 2020 8:51 PM   Subscribe

My dog is already diagnosed with hypothyroidism and has been on medication for a year. He has a checkup tomorrow morning and I can’t remember how I’m supposed to prepare him for a blood test.

I usually give him his thyroid meds in the morning with food. His appointment is at 10:30 am. My recollection is that I should give him his pill about 4-5 hours before his appointment and not feed him until after the appointment. His vet is closed so I can’t ask them but I know I’ve screwed this up many times in the past and had to come back for retesting. Do I have it right?
posted by otherwordlyglow to Pets & Animals (6 answers total)
No food 6-8hrs. Water is ok
posted by Wichienmaat at 9:46 PM on October 28

Thank you - and what about the timing of the morning pill?
posted by otherwordlyglow at 10:06 PM on October 28

With the appointment that early in the morning I'd just wait till after the test. Thyroid hormone builds up over time, one dose being off isn't a big deal. It won't tank his levels for the test or anything.
posted by AlexiaSky at 11:00 PM on October 28

I think it's probably the T4 test, my dog gets this and we get the timing wrong too and have to go back. Per this web site and several others that came up in a search, down in Monitoring and Adjusting Therapy: "...blood is collected 4 to 6 hours post-pill for T4 measurement. " This is about what I recall from last time, although I think my vet had a preference for one side of the window but that specific I can't recall.
posted by lemonade at 12:15 AM on October 29

I gave it to him at 5 hours before the appointment so I'm hoping we'll be good!
posted by otherwordlyglow at 8:05 AM on October 29

FWIW I'm a physician to humans and it was super weird to me when my veterinarian recently did a T4 test on my cat when we use TSH levels in humans to monitor hypothyroidism. T4 levels will vary day to day but TSH level is stable over days to weeks.
posted by neuron at 9:23 PM on October 29

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