This is a trick question! And to answer it, there are several other questions you should ask yourself first.
Let’s start with the purpose of blood work. If you’re trying to identify problems before they happen, bloodwork actually is not the way to do it. Bloodwork is looking for pathology, which is a fancy word for disease. If your cat, dog, or yourself for that matter, has abnormal bloodwork, that means there’s something going on and you’ve missed the sub-clinical/subtle stage. Subtle things are not regularly detected by bloodwork.
Quick caveat: if you analyze 20 values (like happens in bloodwork), statistically one is going to be abnormal. So… you have to look at what makes sense. If one number is slightly off but there’s no other sign of an issue, then it’s just a statistics error.
For young healthy animals, you can do blood work when you want to.
Some people like to have a baseline. It never hurts. (Except for your wallet of course.)
For older pets, without problems, again, annual bloodwork is useful, and as they age, it is good to detect changes early. But then again, bloodwork looks for overt disease.
Now, for the pets that have something going on (for example, pets with kidney disease or liver issues) it’s important to get repeat bloodwork every 1 to 6 months. More frequently when you, the owner, detect changes in behavior.
But if you want to “screen for cancer” in your older pet, routine bloodwork is not the way to do it – routine bloodwork doesn’t detect cancer.
There are other tests from other labs for that. Unfortunately, most conventional vets don’t run those tests. I believe it’s because we don’t learn about it in vet school. That’s just my guess though.
If you want bloodwork and can afford it, go for it. Just try to keep in mind that it only measures a few organs (liver, kidneys, pancreas, blood) and usually only detects overt disease.
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Still seeing patients in Tampa, Clearwater, and virtually.