Blood Tests
Reading Your Cat's Blood Test
What do the H, L, and reference ranges on the report mean? Why do numbers differ between clinics? Understanding these basics first makes each individual value easier to read.
Where reference ranges come from
The reference range printed next to each test is calculated from results of a group of healthy animals, keeping the middle 95%. That means about 5% of results from completely healthy animals fall outside the range (about 2.5% high and 2.5% low). A value that is only slightly outside the range does not automatically mean illness; what matters is how far off it is, whether there are symptoms, and whether other values change too.
Why ranges differ between clinics
Reference ranges depend on the analyzer, the test method, and the species, and cats and dogs have different ranges. That is why this site does not list fixed "normal values". Always use the range printed on your own report. To compare results over time, it is best to test at the same clinic on the same machine.
Trends matter more than a single number
For some tests, such as creatinine, each cat's own usual level varies a lot, and research suggests comparing with that cat's previous values. Even if a cat's creatinine is still within the range, a clear rise compared with its earlier results is worth discussing with your vet. Keep every report so you can follow the changes.
Things that can affect results
Glucose and urea can rise after a meal, so some tests require fasting; for example, the International Renal Interest Society (IRIS) stages kidney disease using fasting values. When a cat is stressed at the clinic, glucose and white blood cells can rise temporarily. If a sample sits too long or becomes hemolyzed, some values can also change falsely.
One abnormal value is not a diagnosis
Vets read blood results by looking at several values together, along with symptoms, the physical exam, and a urine test. For example, creatinine and urea are usually read together with urine specific gravity to tell dehydration apart from a kidney problem. The explanations on this site are meant to help you understand the report before and after a visit; diagnosis and treatment remain your vet's decision.
Practise with real reports →
Three clinics and three cats: how kidney markers, glucose, pancreatic lipase and blood counts inform clinical questions.
Which markers matter for which clinical questions?
A reading order for veterinary visits, not a chart for self-diagnosis.
Kidney function and CKD
CREA and SDMA give kidney clues; BUN has other influences. Diagnosis and staging need urine findings, hydration and stable repeat testing.
Diabetes versus stress-related glucose
GLU is a snapshot; FRU covers longer-term glucose. Discuss persistence, symptoms, urine glucose and monitoring rather than diagnosing from one high result.
Pancreatic involvement
Identify the assay and units, then consider symptoms and imaging. Different methods or cats do not make one trend.
Anemia and bleeding
HCT reflects red-cell proportion; PLT contributes to hemostasis. Reticulocytes, smears and clumps help separate real changes from specimen issues.
Inflammation, infection and white-cell changes
WBC is the total, NEU a subset. Absolute counts and smear findings add clues, but do not identify a pathogen by themselves.
Test-by-test guide
This site does not list fixed normal values: reference ranges differ by analyzer and method, so always use the range printed on your report.
Kidney
Creatinine (CREA)
One of the most common kidney function tests, reflecting how well the kidneys filter blood. It is used to stage kidney disease in cats, but it can underestimate problems in cats with low muscle mass.
SDMA (Symmetric Dimethylarginine)
A newer kidney marker that is not driven by muscle mass like creatinine, so it may detect declining kidney function earlier. It can also be high for unclear reasons, so a recheck is often needed.
Blood Urea Nitrogen (BUN)
A waste product of protein breakdown that the kidneys remove. Diet, dehydration, and gut bleeding also affect it, so it is usually read together with creatinine.
Phosphorus (PHOS)
Often rises when kidney function drops and is a key part of kidney disease care. It is naturally higher in young animals and can also rise in hyperthyroid cats.
Liver
Alanine Aminotransferase (ALT)
An enzyme found mainly inside liver cells that leaks into the blood when those cells are injured. It is also often raised in hyperthyroid cats.
Alkaline Phosphatase (ALP)
An enzyme linked to bile flow and bone activity. Cat livers contain little ALP and it lasts only about 6 hours in a cat's blood, so even mild increases in cats deserve attention.
Glucose & thyroid
Blood Glucose (GLU)
The level of sugar in the blood. Glucose can rise temporarily when a cat is stressed at the clinic, so a single high value is not necessarily diabetes and often needs other tests to confirm.
Thyroxine (T4)
The most common screening test for hyperthyroidism, a frequent disease in middle-aged and older cats. Other serious illnesses can push T4 down so that results look normal.
Fructosamine (FRU)
Helps assess sustained versus brief stress-related high glucose; not measured in the supplied extracts.
Pancreas
Blood cells
Hematocrit / Packed Cell Volume (HCT / PCV)
The share of the blood made up of red blood cells and the main measure of anemia. Dehydration can make it falsely high, and IV fluids can make it lower.
White Blood Cells (WBC)
The total count of immune cells. Which type of white cell is changing matters more than the total, and a cat's count can rise temporarily when it is stressed at the clinic.
Platelets (PLT)
Linked to bleeding risk; confirm feline low counts and check for clumps.
Neutrophils (NEU)
A useful white-cell subset; a normal total WBC can coexist with low NEU.
Related guides
Sources:
- eClinpath — Reference intervals
- eClinpath — SDMA
- IRIS — Staging of CKD (Modified 2026)
- eClinpath — Glucose
- eClinpath（Cornell University）— Quick test interpretation: Chemistry
This site is for general reference only and is not a substitute for veterinary diagnosis. If your cat shows unusual signs, please see a vet promptly.