Does a high value mean my animal is ill?

Not necessarily. A reference interval contains 95 per cent of healthy animals by construction, so one in twenty falls outside it while being perfectly well. What counts is the size of the deviation, whether it agrees with the other analytes, and whether there are any signs. An isolated value barely over the limit in an animal that seems fine usually leads to nothing more than a recheck a few weeks later.

Why does the new laboratory give different values from the old one?

Because different analysers and analytical methods produce results that are not interchangeable, and every laboratory calculates its own reference intervals from its own population and technique. That is why animals under long term monitoring are ideally tested at the same provider. If you have to change, the first result at the new laboratory becomes the new baseline, not evidence of deterioration.

My cat had high blood glucose: is that diabetes?

You cannot conclude that from a single sample. In cats the stress of travel and handling raises glucose within minutes, sometimes past 200 mg/dl, with no diabetes present at all. To separate stress hyperglycaemia from the real thing, vets use fructosamine, which reflects the preceding weeks, urine glucose testing, and the presence of signs such as increased thirst and urination.

Should the animal fast before the blood sample?

In most cases yes, usually eight to twelve hours, always with water available. Circulating fat after a meal turns serum milky and skews several analytes, and glucose measured after eating cannot be interpreted. There are important exceptions, such as very young puppies and kittens and diabetic animals on insulin: for those, ask the clinic for specific instructions before withholding food.

Is there any point testing an animal that seems healthy?

There is, in two situations. The first is before anaesthesia, to find problems that would change the protocol. The second is routine monitoring of older animals, broadly from seven years of age in dogs and cats, where the aim is not to find disease today but to build the historical series that will let somebody recognise a real shift two years from now.

Health management30 minLevel: AdvancedUpdated on August 1, 2026

Reading a blood test report without panicking

What a laboratory report contains, how to read a blood count and a biochemistry panel, and why one value outside the range is not yet a diagnosis.

Audience: Pet owners
Species: Dog, Cat
Scope: Valid everywhere

What you need before you start

Il referto completo, comprese le pagine con le note del laboratorio e le condizioni del campione
I referti precedenti dello stesso animale, se esistono, per poter confrontare
L'elenco dei farmaci in corso, perché molti alterano i valori del sangue
L'orario dell'ultimo pasto prima del prelievo e le condizioni in cui è stato fatto

The report almost always arrives before the explanation: handed to you at reception, or emailed on a Friday evening, with three lines in bold and an arrow pointing up. From there to an online search is a very short step, and an online search always returns the worst diagnosis that fits. This guide exists to break that chain: to show how a report is built, which analytes appear nearly every time, and why a single value outside the range settles nothing on its own. It does not replace your vet's interpretation, it turns that interpretation into a conversation between people speaking the same language.

What a report actually contains

Every laboratory report shares the same structure underneath very different layouts. Recognising it in thirty seconds stops you from reading only the highlighted lines, which are the ones that frighten but not always the ones that matter.

Identification: animal name, species, breed, age, sex and owner. Check this first, because a wrong reference interval nearly always starts with a species entered incorrectly.
Sampling date and time, separate from the analysis date: hours can pass between the two, and some measurements shift with storage time.
The list of analytes, each with its value, unit of measurement and the laboratory's own reference interval.
Automatic flags, usually an arrow or a letter beside any value outside the range. They are generated by the analyser, not by a person.
Sample condition notes: haemolysis, lipaemia, icterus. These are technical remarks explaining why some values may be unreliable.
The clinical pathologist's comment where one is provided: the most valuable part of the report and almost always the least read.

Reading the complete blood count

The blood count measures the cells in blood. It answers three questions: are there enough red cells to carry oxygen, is the immune system reacting to something, are there enough platelets to stop a bleed. The intervals below are indicative and exist to orient your reading: the binding one is always printed next to the value on your own report.

Blood count analytes that appear almost every time, with indicative intervals for adult dogs and cats. Every laboratory publishes its own, and those are the ones that count.
Analyte	Dog	Cat	What it reflects
Haematocrit	37 to 55 per cent	30 to 45 per cent	Share of blood made up of red cells: low suggests anaemia, high suggests dehydration
Haemoglobin	12 to 18 g/dl	9 to 15 g/dl	Oxygen carrying capacity, moves together with the haematocrit
Total white cells	6.0 to 17.0 thousand per microlitre	5.5 to 19.5 thousand per microlitre	Immune system activity, rising in many inflammatory and infectious processes
Neutrophils	3.0 to 11.5 thousand per microlitre	2.5 to 12.5 thousand per microlitre	The fraction that most often rises with acute inflammation
Lymphocytes	1.0 to 4.8 thousand per microlitre	1.5 to 7.0 thousand per microlitre	Fall with stress and with steroids, rise in some chronic conditions
Platelets	200 to 500 thousand per microlitre	300 to 700 thousand per microlitre	Ability to form a clot: in cats they clump easily and get underestimated

Reading the biochemistry panel

The biochemistry panel measures substances dissolved in serum and describes how kidneys, liver and metabolism are working. It is the part of the report that causes the most alarm, because many analytes move for reasons that are trivial and temporary.

Core biochemistry analytes with indicative intervals for adult dogs and cats. The binding reference stays the one printed on the report.
Analyte	Dog	Cat	What it reflects
Creatinine	0.5 to 1.5 mg/dl	0.8 to 2.0 mg/dl	Kidney function, but it only rises once roughly 75 per cent of function is already lost
Urea	8 to 28 mg/dl	15 to 35 mg/dl	Moves with the kidneys but also with diet, dehydration and intestinal bleeding
SDMA	Up to 14 micrograms per dl	Up to 14 micrograms per dl	An earlier kidney marker, it shifts before creatinine does
ALT	10 to 100 U/l	20 to 100 U/l	Liver enzyme: rises when liver cells are stressed, without saying why
Alkaline phosphatase	20 to 150 U/l	10 to 90 U/l	In dogs it rises easily with steroids and during growth, in cats it is more specific
Glucose	70 to 120 mg/dl	70 to 150 mg/dl	In cats it rises from the stress of sampling alone, sometimes past 200 mg/dl
Total protein	5.4 to 7.5 g/dl	5.7 to 8.0 g/dl	Rises with dehydration and with chronic inflammation
Albumin	2.6 to 4.0 g/dl	2.5 to 3.9 g/dl	Falls with intestinal or renal losses and with advanced liver failure

One practical rule helps more than any table: a single analyte slightly outside the range rarely means anything, whereas two or three analytes that agree with each other tell a story. Creatinine and SDMA both raised, alongside dilute urine, point at the kidneys; a creatinine barely over the limit in a muscular, dehydrated dog after a run very probably does not.

Why one value outside the range is not a diagnosis

A reference interval is not the boundary between healthy and ill. It is built by measuring a group of healthy animals and taking the central band containing 95 per cent of results. That has a counterintuitive consequence: roughly one healthy animal in twenty falls outside the range for any given analyte. On a panel of twenty analytes, the chance that a perfectly healthy animal has at least one flagged value is very high.

Fasting: without at least eight hours the serum can be lipaemic and skew several analytes.
The stress of travel and restraint: in cats it raises glucose and white cells within minutes.
Haemolysis, meaning red cells breaking in the tube, which alters potassium and several enzymes.
Age and growth stage: in puppies and kittens alkaline phosphatase is physiologically higher.
Breed: some northern breeds run higher haematocrits, and sighthounds have their own values for several analytes.
Medication in progress, from corticosteroids to antiepileptics, which persistently shift certain enzymes.
The laboratory and the analyser: two different machines produce values that are not interchangeable on the same sample.

The questions to ask your vet

The phone call about results lasts a few minutes and should be used well. These six questions, asked in this order, cover almost everything you need in order to decide the next step.

Which values in this report are clinically important
Ask them to separate values flagged by the analyser from values that genuinely change the assessment. There are usually few of them, and they do not always match the ones printed in bold.
How far outside the limit is it
A value just over the limit and a value three times the limit mean entirely different things. Ask for the order of magnitude, not just the word high.
Does this fit what we are seeing in the animal
An abnormal value in an animal with no signs leads to a different course of action than the same value in one that is losing weight and drinking heavily. This question ties the number back to reality.
Could this come from how the sample was taken, or from a drug
Fasting, stress, haemolysis and current treatment explain a sizeable share of abnormalities. If the answer is yes, the next step is often simply repeating the test under better conditions.
What changes now, and what happens if we do nothing
Ask for both paths to be described. Knowing what risk you run by waiting is the information that lets you decide together rather than have a choice imposed.
When do we repeat the test and what do we expect to see
Fix the recheck date before you leave and ask which change would be reassuring and which would be concerning. The next report then takes thirty seconds to read.

Following the trend over time

A single value is a photograph, a series is a film. In practice almost every important decision comes from comparing successive reports, not from one isolated number. Building that series takes a little discipline, otherwise the comparisons are not valid.

Keep every report in one place, in date order and in a readable form, not as crooked photographs.
Repeat tests at the same laboratory where you can, because intervals and methods differ between providers.
Sample under the same conditions: same time of day, same fasting period, same distance from meals.
Note beside each report the weight, the treatment in progress and the signs present at that moment.
Copy into a table of your own the three or four analytes your vet flagged as relevant for your animal.
Bring the whole series to every recheck, even when it feels like nothing has changed.

Frequently asked questions

Does a high value mean my animal is ill?: Not necessarily. A reference interval contains 95 per cent of healthy animals by construction, so one in twenty falls outside it while being perfectly well. What counts is the size of the deviation, whether it agrees with the other analytes, and whether there are any signs. An isolated value barely over the limit in an animal that seems fine usually leads to nothing more than a recheck a few weeks later.
Why does the new laboratory give different values from the old one?: Because different analysers and analytical methods produce results that are not interchangeable, and every laboratory calculates its own reference intervals from its own population and technique. That is why animals under long term monitoring are ideally tested at the same provider. If you have to change, the first result at the new laboratory becomes the new baseline, not evidence of deterioration.
My cat had high blood glucose: is that diabetes?: You cannot conclude that from a single sample. In cats the stress of travel and handling raises glucose within minutes, sometimes past 200 mg/dl, with no diabetes present at all. To separate stress hyperglycaemia from the real thing, vets use fructosamine, which reflects the preceding weeks, urine glucose testing, and the presence of signs such as increased thirst and urination.
Should the animal fast before the blood sample?: In most cases yes, usually eight to twelve hours, always with water available. Circulating fat after a meal turns serum milky and skews several analytes, and glucose measured after eating cannot be interpreted. There are important exceptions, such as very young puppies and kittens and diabetic animals on insulin: for those, ask the clinic for specific instructions before withholding food.
Is there any point testing an animal that seems healthy?: There is, in two situations. The first is before anaesthesia, to find problems that would change the protocol. The second is routine monitoring of older animals, broadly from seven years of age in dogs and cats, where the aim is not to find disease today but to build the historical series that will let somebody recognise a real shift two years from now.

What to do next

Before reading the highlighted lines, check the species, the sampling date and the sample condition notes, then look at whether the abnormal analytes tell a coherent story instead of reading them one by one. Take the six questions to your vet, book the recheck straight away, and keep every report in order in the same place: the series over time is worth far more than any single number.