How Often Should Dogs Have Blood Tests? A Vet’s Guide by Age and Size

How often your dog should have blood tests depends on their age, size, breed, medical history and overall health.

For healthy small and large-breed dogs, I generally recommend starting annual blood screening from around eight years of age. For giant breeds, I may start earlier, at approximately five to seven years. As dogs become older, I usually recommend more frequent screening, sometimes every six months or every three to six months in very elderly dogs.

These are my usual clinical recommendations rather than fixed rules. A younger dog with an existing medical condition, concerning symptoms or certain medications may need testing much earlier. I also prefer to assess blood results alongside urine testing and a thorough physical examination, because each provides different information about your dog's health.

Does every young dog need routine blood tests?

I don't routinely recommend annual blood tests for every healthy dog under five years old. If a young dog is well, has no relevant medical history and has a normal examination, there may be little reason to repeat a full blood panel every year.

That changes if a dog is unwell or there is something we need to investigate. Vomiting, diarrhoea, weight loss, increased thirst, reduced appetite and unusual tiredness are all possible reasons to recommend blood tests, regardless of age. Testing may also be appropriate before anaesthesia, when monitoring long-term medication or if we suspect a toxin exposure.

Even in a healthy younger dog, an individual baseline can be useful when there is a particular medical reason to obtain one. The decision should be made with your veterinarian, rather than based on age alone.

How often should small dogs have blood tests?

For smaller dogs, these are the intervals I commonly recommend when they are otherwise well:

Some small dogs remain active and well into their mid-to-late teens. However, they can still develop kidney disease, diabetes and other conditions without showing obvious symptoms at first. Screening becomes more useful as the likelihood of these problems increases.

How often should large dogs have blood tests?

Large-breed dogs often show age-related changes earlier than smaller dogs. Although I usually begin annual blood screening at around eight years of age, I tend to increase the frequency earlier:

I would bring testing forward if the dog were losing weight or muscle, becoming less active, eating less enthusiastically, drinking more water or developing any other change that concerned me.

For medium-sized dogs, I consider the breed, expected ageing pattern and the individual dog's health rather than using a separate schedule with rigid age cut-offs.

How often should giant-breed dogs have blood tests?

Giant breeds tend to have shorter average lifespans and can develop age-associated problems at a younger chronological age. For dogs weighing approximately 45 kg or more as adults, my usual approach is:

These age ranges are a guide. I would adjust them based on the individual dog's breed, previous test results and clinical condition.

Why test a healthy dog? The value of routine screening

Some illnesses develop gradually, and dogs can compensate for changes in their health surprisingly well. By the time an owner notices a reduction in appetite, increased drinking, weight loss or weakness, a problem may already be well established.

Routine screening gives us an opportunity to look for changes before they become obvious at home. When we find something early, we may have more options to investigate the cause, begin appropriate treatment or monitor the condition more closely.

Chronic kidney disease is one example. In an early stage, a dog may have very few outward signs, yet blood or urine testing may already suggest that the kidneys need closer assessment. We can then check blood pressure, urine concentration and protein loss, consider imaging where appropriate, and establish a monitoring plan. How long a dog remains well varies greatly, but an earlier diagnosis can give us more time to respond to meaningful changes.

Routine blood tests cannot detect every disease, and a normal result is not a guarantee that a dog is healthy. They are most useful when we interpret them as part of a broader health assessment.

What does routine dog blood work check?

A typical screening panel includes a complete blood count and blood biochemistry. Together, these can provide information about:

• Red blood cells, white blood cells and platelets.
• Kidney and liver markers.
• Blood glucose.
• Protein levels and electrolytes.

Depending on the dog, I may also recommend additional tests such as SDMA or thyroid testing. The exact panel should depend on what we are trying to assess, rather than automatically including every available marker.

Blood tests are especially useful when combined with urinalysis. For example, a change in kidney markers means more when we also know how well the dog is concentrating their urine. Blood pressure, body weight, muscle condition and relevant imaging can provide further information.

If you'd like a more detailed explanation of individual markers, see our guide to longevity blood tests for dogs.

Why I compare your dog's blood results with previous tests

When I review blood results, I don't look only at whether each value falls within the laboratory's reference range. I also compare the results with previous tests to see whether anything has changed over time.

For example, a dog's creatinine may still be within the reference range but have increased gradually compared with its previous readings. That doesn't automatically mean the dog has kidney disease, but I would want to understand the change. I would review the dog's hydration, weight and muscle condition, appetite, drinking and urination habits, and urine results before deciding whether to investigate or repeat the test.

The same principle applies to changes in red blood cell counts, liver markers and other measurements. Sometimes a difference is caused by normal biological variation or a temporary illness. In other cases, the trend may be more useful than a single abnormal result.

I also pay attention to what owners have noticed at home. A blood report is only one part of the picture; a gradual change in appetite, stool quality, mobility or weight can provide important context when we interpret it.

Can blood tests detect cancer?

Blood tests cannot reliably detect or rule out cancer in dogs. Some cancers may cause changes such as anaemia, altered liver values or abnormalities in other blood cells, but many dogs with cancer have fairly unremarkable routine blood results.

If I find an unexpected abnormality, I may recommend further investigations. For example, significant anaemia could lead us to look for possible blood loss, including bleeding within the abdomen. An ultrasound or X-ray may help identify an underlying cause, depending on the findings.

A physical examination also remains essential. Blood testing cannot replace checking the heart and lungs, examining the mouth, feeling the abdomen, assessing lymph nodes or evaluating a dog's joints and muscles.

Do all dogs need to follow these schedules?

Not necessarily. A dog with stable health may have different needs from one with chronic kidney disease, diabetes or a history of abnormal test results. Dogs taking certain long-term medications may also need more frequent monitoring.

The schedules above describe my usual approach to screening dogs that are otherwise well. They are not a reason to wait if your dog becomes unwell between planned appointments.

Contact your veterinarian promptly if your dog is losing weight, eating less, vomiting repeatedly, having persistent diarrhoea, drinking or urinating more than usual, or becoming unusually weak or lethargic. If your dog collapses, cannot stand or is severely unwell, seek urgent veterinary care.

Preparing for your dog's blood test: Fasting and turnaround times

Do dogs need to fast before a blood test?

Most normal routine panels run in-house do not require fasting. However, a 12-hour fast is needed for certain blood tests (such as specific bile acid or triglyceride assessments) — always ask your vet clinic ahead of your appointment. Fresh water should never be withheld unless your vet gives specific instructions before surgery or sedation.

How long do blood test results take?

Routine screening panels run on in-house clinic analysers can often be reviewed during your consultation or later the same day. Any specialised tests sent out to an external laboratory take an average of 1 to 2 weeks to come back.

Bring your dog's previous blood and urine results if they were done at another clinic. It is also helpful to know your dog's recent weight, exact diet and treats, medications, supplements, appetite and toileting habits, and whether anything has changed at home.

For older dogs, I would much rather investigate a gradual change while your dog still feels reasonably well than wait until they are obviously unwell. The right screening schedule is the one that reflects your dog's age and individual health, with adjustments as their needs change.

What to Do This Week

Look at your dog's age, size and health history, and check when their last blood and urine tests were done. If they are due for screening, arrange a visit with your veterinarian to discuss a schedule that suits your dog — and bring any previous results so trends can be compared.

When to See a Vet Urgently

Contact your veterinarian promptly if your dog is losing weight, eating less, vomiting repeatedly, having persistent diarrhoea, drinking or urinating more than usual, or becoming unusually weak or lethargic. If your dog collapses, cannot stand or is severely unwell, seek urgent veterinary care.

This article is for educational purposes only and does not replace professional veterinary advice. If your dog is unwell, please consult your veterinarian.

Screening is one part of a wider picture; read more on helping dogs age well.