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Does my dog need to fast before a thyroid blood test? How long?

Updated On September 23rd, 2025

Pet's info: Dog | Mixed Breed Small (up to 22lb) | Male | neutered | 4 years and 9 months old | 17 lbs

My dog has a thyroid level test tomorrow at 1015. I forgot to ask if he should fast beforehand and if so how long before? Do dogs need to fast for this?

2 Answers

Most Helpful Answer

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Answered By Dr. Melanie, BVSc MS

Veterinarian

Published on February 6th, 2019

Thank you for contacting Pet Coach with your question about Charlie. I would not feed him breakfast in the morning until after his blood is drawn. Samples can be too fatty if the blood is taken too soon after a meal. He can have water, but hold off on feeding him in the morning. I hope this helps!

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4Pet Parents found this answer helpful

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    Answered By Dr. Dayna, DVM, CVA

    Veterinarian, Certified Veterinary Acupuncturist

    Published on May 20th, 2018

    Hi there! Great question! I typically just have my patients skip breakfast, so at least a 12 hour fast, however don’t withhold water. You can feed breakfast after the blood draw. Best of luck and thank you for using Pet Coach.

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    1Pet Parents found this answer helpful

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