What Are Pet Blood Tests For?

Updated November 29, 2020

You’ve probably noticed how much we like blood tests. Every year when your dog or cat has their annual checkup or when your pet needs an anaesthetic we ask you if you want blood testing.

Is this just over-servicing or are there good reasons to check?

In the end it’s up to you to decide. Once you read Trixie’s story you may see it from our point of view.

Why Do We Do Blood Tests?

trixie at vet

Two years ago when Trixie was ten years old, she came for her annual checkup. She seemed completely healthy but when we asked her owner if she also wanted us to take blood she said yes. Here’s why:

  • The older you are the more can go wrong
  • Dogs age seven times faster than humans; each annual checkup spans seven of our years
  • Dogs can’t complain about feeling sick
  • Good haemoglobin, kidney & liver values are vital for anaesthetics
  • And what most pet owners say: we’d do it for ourselves

What Do Blood Tests Look At?

Trixie’s physical exam was 100% normal but we didn’t stop there. Our nurses do a great job of holding dogs or cats for blood testing, and so the sample was taken without distress to dog or owner.

Although we have our own in-house blood analytical machine for emergency and pre anaesthetic screening, we always send non urgent samples to an external laboratory.

dog blood test

Here are Trixie’s results. I’ve labelled each set of values so you can see what is included in a standard blood test. As you can see, there are a lot of readings taken from a tiny amount of blood.

We can get all of this from 1.5mL of blood. If you look at the second test you’ll see there’s even more. Sometimes I stop to remember how amazing this is.

As you can see, each value is reported with the normal range for that parameter. As you can also see, there are some abnormalities.

The job of the vet is to sort the wheat from the chaff. There are always spurious or irrelevant abnormalities. In this case, though, you can see that no-one would look at those liver enzymes and think they are OK.

Next problem:

What Happens With Abnormal Blood Results?

The first thing you need to know is that we will always call you to discuss blood results, whether they are normal or not. If you don’t hear from us within two days, check that we’ve got your best phone number, because you can bet we’ve tried.

Most of the time, abnormal results don’t give us a diagnosis. We find that something isn’t working properly or that an organ is in trouble. We still need to find out why.

Typical blood test
Trixie’s second blood test results

Most abnormal results will result in us asking for further specific testing. Often we’ll ask you to collect a urine sample. In Trixie’s case, we started with a second blood test for Cushings Syndrome (which was negative), and then recommended an ultrasound examination.

The ultrasound showed a large mass in the liver, but indicated that there was still time to remove it. She had routine surgery to remove the mass inside its liver lobe.

Recently I saw her again and did her annual checkup. That’s her above looking fantastic. No surprises that her owner asked for another blood test. This one is a good example of the minor variations we can safely disregard.

Should My Dog Or Cat Have Blood Tests?

I like to think of blood testing as a fishing trip. You don’t know what you’re going to catch, and often you come back with nothing to show for the effort and cost (the price of Trixie’s test is listed here).

Read here how often pet blood tests are abnormal. It’s a gamble being played with very high stakes. If Trixie didn’t have her routine blood test we would never have found the tumour in time, and she would not be alive and happy today.

Common and important findings include kidney disease, liver disease, chronic pancreatitis and hormonal diseases like overactive or underactive thyroid, diabetes or cushing’s syndrome. All of these can be managed if we discover them in time. Many of them also affect how your pet copes with an anaesthetic.

Most of the time, blood testing will not be this dramatic, but we regularly see stories like Trixie’s. In the end, we will never tell you you should get blood testing done. It’s always your choice and we respect that. But I’ll bet there aren’t many vets who don’t do it for their own animals.

Have something to add? Comments (if open) will appear within 24 hours.
By Andrew Spanner BVSc(Hons) MVetStud, a vet in Adelaide, Australia. Meet his team here.

7 Replies to “What Are Pet Blood Tests For?”

  1. Our 14 year old dog unfortunately got diagnosed with blood cancer earlier this year, from a CBC. It showed about 50k WBC wereas 60% looked cancerous (lymphoblasts) according to IDEX pathologists. We did this test last couple of years every annual check up, and before last time we did it also just 4 months prior she got sick (then because of an UTI). The blood test was normal then.

    don’t know if its rare to diagnose cancer from a blood test, because your not mentioning it in your list.
    She was diagnosed stage 4 lymphoma _leukemia, in her spleen and blood, and got very bad in less then a weeks time from first symptom (fever). Didnt eat, had a hard time walking normally and started breathing heavy. Tragiclly We were forced to let her go because of anemia.

    1. Hi John. You’re right – it is unusual in dogs to diagnose cancer from a blood test alone, as most lymphoid tumours are solid tissues, not in the bloodstream like leukaemia. I’m sorry for your loss.

  2. H, my Jack Russell is going to be desexed and the Vet clinic has emailed me with additional extras: a blood tests prior to the procedure and intravenous fluids during the op. These are optional extras that are addition costs. My JR is 6 months and has no obvious health problems. Should I say yes to the ‘optional extras’ which double the cost of desexing? I’m in NZ $260 for desexing + $260 for both extras. I would appreciate your thoughts. Thanks for the great website and blogs which I often refer to. An Aussie living in NZ

    1. Hi Leone. If your dog is under a year of age and healthy, you can consider blood testing as optional. It’s not common that are problems found that would change or delay the anaesthetic so the risk of missing something is reasonably low. As for the cost of the drip, you will probably find that other vets include this as a standard in desexing – I certainly think that if you really believe something is necessary it should not be an option.

  3. Hello,
    I have a 6 and half year old female Chinease Sharpei, about 3 years ago she started having these episodes I do not know how to explain it, she tenses and cannot move, like an epilepsy attack but her whole body pulls tight and she cannot walk or stand but she is aware of us that are around her and after a while it stops and she is back to normal. So I took her to a few Vets and nobody can explain what it is, they put her on Valium but I decided not to give her that medication because the attacks are not often maybe once every 3 months, so 1 vet requested blood tests but he can’t tell us what is wrong with her. When she as an attack we sit with her and calm her down, talking to her the whole time and letting her know that she will be okay and it passes. What do you think could be wrong because the Vets in my area cannot give me an answer. She is otherwise a happy normal healthy bossy little girl. She eats well, very active, so we just want to help her more if it is possible and another Vet prescribed a pill called Lethal and she must have that for the rest of her life, I don’t know if it is necessary to put her on pills everyday, I am sure it will have a negative effect on her organs at some point but I am not an expert so any advice will be my highly appreciated. Thank you

    1. Hi Chrisanne. Although I can only guess from this distance, the episodes you are describing sound most like focal or partial seizures. You can find information on them in our page on seizures. If I am right, they usually don’t show up on a blood test, aren’t easily treated, and may in fact not be like regular seizures at all. What you are doing sounds sensible and given that they only happen every few months (and I hope only happened for a few minutes each time) I think your approach is quite suitable.

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