ProBNP is a protein biomarker released when a cat's heart muscle is under stress or stretched abnormally. Veterinarians use blood tests measuring NT-proBNP levels to screen for cardiac disease in cats, especially hypertrophic cardiomyopathy, which affects roughly 15% of cats and often shows no outward symptoms until advanced stages. Normal feline NT-proBNP levels typically fall below 100 pmol/L. Values between 100-270 pmol/L suggest possible heart disease requiring follow-up echocardiography, while readings above 270 pmol/L indicate significant cardiac abnormality. The test catches problems early because the heart releases this peptide when ventricular walls thicken or chambers enlarge, long before cats show breathing difficulty or lethargy. Veterinarians commonly order proBNP testing in several scenarios: pre-anesthetic screening for cats over 6 years old, evaluation of heart murmurs detected during routine exams, breeds predisposed to HCM like Maine Coons and Ragdolls, and cats showing subtle signs like reduced activity or occasional rapid breathing. The blood test costs between CAD 150-250 at most Canadian veterinary clinics and provides results within 24-48 hours through reference laboratories. The test isn't perfect. False negatives occur in very early disease stages, and some cats with mildly elevated levels never develop clinical heart failure. Stress, kidney disease, and hyperthyroidism can also influence readings. That's why veterinarians interpret proBNP alongside physical examination findings, chest x-rays, and echocardiography rather than relying on the number alone. For cat owners, proBNP testing offers a non-invasive way to identify heart disease before emergency situations develop. Early detection allows for medication that can slow disease progression and extend quality of life, though it cannot cure underlying structural heart problems. Most cardiologists recommend repeating the test every 6-12 months in cats with borderline elevations to track progression.