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Geriatric Blood Screening - What happens in a blood test?

Have you got a senior pet? We class large-breed dogs over six years and most dogs over eight years to be senior, whilst cats aren’t senior until they’re over ten years. As they progress to geriatric (cats 14 years, dogs 9-12 years) illnesses become more and more common. Did you know that 1 in 3 cats will suffer from kidney problems? Or that 10% of dogs will get heart disease related to ageing? It can be hard to diagnose though, as dogs, and especially cats, are really good at hiding signs of ageing and disease.

That’s why we recommend blood screening for our older patients. We can check their blood for markers of many diseases that older pets are prone to, and it’s a great way to get a good picture of their overall health. Bloods should be taken before an anaesthetic, if animals become ill, or if they are on medications. They can also be taken in older pets that appear healthy in order to catch diseases before they develop symptoms.

What happens in a blood test?

We will take your pet through to our prep room to be steadied by a veterinary nurse experienced in holding animals for this procedure. Most animals do not get overly stressed by this. Some cats, especially those that are known to be stressed at the vets, may benefit from a small amount of sedation before taking blood, but we will discuss this with you if we feel this would be necessary. Blood is usually taken from the jugular vein, under the neck, and you may notice that we’ve clipped a small area of fur here to enable us to see the vein more easily. In large-breed dogs or dogs with skin folds around the neck, we may use the front or back leg vein instead. We clean the area, then use a small needle and syringe to collect around 2ml of blood (about half a teaspoonful). This is placed into several bottles and mixed. A nurse then runs the sample through our machines, which read various chemicals in the blood and recognise different blood cells. The entire process can take as little as half an hour, but unless your results are urgent we usually suggest that a vet will phone you to discuss the results at a later time.

What do the results mean?

We appreciate it can be hard to understand what these blood tests are for and what we think when we get the results, so this is a quick guide to some of the more common senior illnesses and how they might show up on our blood screens.

Kidney Disease

Kidney disease is very common in older pets, affecting about 1 in 3 cats and 1 in 10 dogs. It can have subtle symptoms so it’s important that we test for it. When we test your pet’s blood with renal disease in mind, we’re looking for changes in urea and creatinine, two of the things the kidneys remove from the body. We may also see changes in the red blood cells (such as anaemia).



Hyperthyroidism is another common disease of cats, affecting about 1 in 10 geriatric cats. It occurs when the thyroid gland gets a benign tumour, and this tumour makes too much thyroid hormone. Although symptoms can be obvious, it’s important for us to measure the level of thyroid hormone so that we can assess the response to treatment. Other than increased thyroid hormone, cats with hyperthyroidism may also have blood results that suggest liver or heart problems due to the stress placed on their bodies.


Cushing’s is a common disease in older dogs. The symptoms can be extremely subtle and put down to old age. We’ve often diagnosed Cushing’s disease on blood tests and owners only recognise the subtle symptoms after we discuss the disease with them. Our geriatric screen doesn’t test specifically for Cushing’s, but changes in the liver can hint at a problem for us to investigate further.

Interpreting the Results

As you can see, it’s not as simple as running lots of tests that are either positive or negative for every disease. Many of these test results indicate lots of different diseases, and it’s only with careful interpretation and comparison with your pet’s symptoms and history that we can decide how relevant these results are.

So next time you bring your senior pet in for a check over, ask us about our geriatric screens. If we catch a disease early, we’re one step ahead. And if your pet gets the all-clear, then that’s a weight off your shoulders. We can also use the results gained as a baseline, so next year if something has changed, we’ll be able to spot it.

Rushcliffe Vets
Rushcliffe Vets
Geriatric Blood Screening - What happens in a blood test?