A 17 item chemistry panel is not 17 separate answers. It is 5 clusters: kidney, liver, protein, mineral and electrolyte. The 7 rows that decide most feline cases are BUN, creatinine, ALT, ALP, GGT, phosphorus and calcium, and 4 of those 7 only mean something when read next to a second row.
What the 17 items actually are
A standard feline panel covers BUN, creatinine, glucose, ALT, ALP, GGT, AST, CK, total protein, albumin, globulin, cholesterol, calcium, phosphorus, sodium, potassium and chloride. SDMA is often added, making 18. A single flagged row in a well cat is a reason to repeat, not a diagnosis.
| Item (unit) | Lower limit | Upper limit | Read it as |
|---|---|---|---|
| BUN (mg/dL) | 16 | 36 | High: dehydration, kidney disease, GI bleed. Low: liver failure |
| Creatinine (mg/dL) | 0.8 | 2.4 | High: kidney disease, obstruction. Low: low muscle mass |
| ALT (U/L) | 20 | 100 | High: liver cell injury, hypoxia, toxins |
| ALP (U/L) | 10 | 80 | High: bile duct disease, bone growth, drugs |
| GGT (U/L) | 0 | 4 | High: biliary disease, cholestasis |
| Glucose (mg/dL) | 74 | 159 | High: stress, diabetes. Low: sepsis, liver failure |
| Total protein (g/dL) | 5.7 | 8.9 | High: dehydration, inflammation. Low: protein loss |
| Albumin (g/dL) | 2.2 | 4.0 | High: dehydration. Low: protein loss, liver failure |
| Calcium (mg/dL) | 8.0 | 11.0 | High: parathyroid, cancer. Low: kidney disease |
| Phosphorus (mg/dL) | 3.1 | 7.5 | High: kidney disease, growing kitten. Low: hyperthyroidism |
BUN and creatinine: read the ratio, not the rows
BUN rises with dehydration before creatinine moves, because urea production depends on protein intake and liver function as much as on filtration. The BUN to creatinine ratio normally sits between 10 and 20. Above 20 with a creatinine of 1.8 mg/dL suggests prerenal azotemia or bleeding into the gut, and a fluid challenge or a repeat sample 24 hours later separates them. Both rows high with a ratio under 10 points to kidney disease itself.
Creatinine is the more specific row but the later one: roughly three quarters of kidney function can be gone before it crosses 2.4 mg/dL. SDMA rises earlier and is reported under 18 ug/dL in most cats. Staging uses creatinine bands: under 1.6 mg/dL is stage 1, 1.6 to 2.8 is stage 2, 2.9 to 5.0 is stage 3, and above 5.0 is stage 4. Those bands are a classification, not a treatment plan, and a single value above 5.0 in a dehydrated cat should be repeated after rehydration.
ALT, ALP and GGT: 3 different questions
ALT leaks when liver cells are injured, so it is sensitive but not specific: a cat with a fatty liver, hypoxia from a heart condition, or a recent seizure can post 200 to 400 U/L and recover. ALP in cats has a short half life of roughly 6 hours, so mild rises of 90 to 150 U/L are often transient and vanish on a recheck 2 weeks later. GGT rises with bile duct disease and is the most specific of the 3, but also the least sensitive.
The pattern matters more than the peak. ALT at 300 U/L with normal ALP and GGT suggests hepatocellular injury. ALP at 400 U/L with GGT at 12 U/L suggests cholestasis or bile duct inflammation. Both ALT and CK high after a struggle during venipuncture suggests muscle, not liver, since CK is muscle specific and a difficult draw can push it past 1000 U/L.
Phosphorus and calcium: the pair that tracks kidney function
Phosphorus above 7.5 mg/dL in an adult cat is abnormal and, with a creatinine above 2.8 mg/dL, is the classic picture of advanced kidney disease. A kitten at 8 weeks can sit at 8 to 9 mg/dL normally, so age matters. Calcium below 8.0 mg/dL is often an albumin artifact: total calcium falls about 0.4 mg/dL for every 1.0 g/dL drop in albumin, so a cat with albumin at 1.8 g/dL and calcium at 7.4 mg/dL may have normal ionized calcium. Ionized calcium, measured separately, runs about 1.1 to 1.4 mmol/L and is the number that matters when tetany or facial twitching appears.
What a high value means across the panel
High values in the kidney cluster (BUN, creatinine, phosphorus) point to reduced filtration, dehydration, or obstruction, and the first question is whether the cat can concentrate urine. High liver values split into leak (ALT), cholestasis (ALP, GGT) and muscle (CK, AST). High glucose above 250 mg/dL in a cat that was not struggling is worth a urine test and a fructosamine, since stress hyperglycemia usually sits between 160 and 250 mg/dL and clears within hours.
High total protein above 8.9 g/dL with high globulin suggests chronic inflammation or a monoclonal gammopathy, while high total protein with normal globulin in a cat that has not drunk for 2 days is simple dehydration.
What a low value means
Low albumin under 2.2 g/dL is the row that changes management fastest, because it points to protein losing kidney disease, protein losing gut disease or liver failure, and it drags total calcium down with it. Low glucose under 74 mg/dL in a cat that is not eating is a same day problem, especially with a low potassium under 3.5 mmol/L. Low BUN under 16 mg/dL matters mainly in a cat with a portosystemic shunt or 3 days of intravenous fluids, where it reflects a liver that is not making urea.
What to ask your vet about the panel
Ask 4 things. Which rows were run in-house and which went to a reference laboratory, since intervals differ between the 2. Was the sample lipemic or hemolyzed, because both distort potassium, phosphorus and ALP. Was urine specific gravity measured alongside the kidney rows, since a creatinine of 2.6 mg/dL with urine at 1.050 means something very different from the same value with urine at 1.015. And is there a 6 to 12 month baseline, because a creatinine that climbed from 1.4 to 2.2 mg/dL across 3 visits is a trend, not a single result.
Recheck intervals that fit the finding
Mild ALT rise under 200 U/L with a normal cat: recheck in 2 to 4 weeks. Creatinine in stage 2: recheck in 4 to 8 weeks with urine protein and blood pressure. Phosphorus above 7.5 mg/dL: recheck in 1 to 2 weeks, not 3 months. Glucose above 250 mg/dL: urine and fructosamine within 3 days. Any single flagged row with no clinical signs: repeat in 2 to 4 weeks before imaging.
Reference intervals differ between analyzers, so compare your cat with the range printed on its own sheet. For why urine concentration matters, see urine marking chemistry; if the cat is a Persian or Exotic Shorthair, the breed quiz lists screening ages for kidney cysts.
Terms mentioned in this article
Frequently asked
Is a creatinine of 2.2 mg/dL kidney failure in a cat?
It sits in stage 2 by the usual bands, but it is not a diagnosis on its own. Ask for urine specific gravity, urine protein and a repeat sample after hydration, because a dehydrated cat can post 2.2 mg/dL and drop back under 1.8 once water is restored.
Why does ALT go up and down so much between tests?
ALT leaks from injured liver cells and clears within days, so it tracks events rather than chronic damage. A cat that had a seizure, a period of poor perfusion or a difficult restraint can show 300 U/L and be back under 100 U/L two weeks later on a recheck.
My cat's calcium is low. Does that mean something serious?
Usually it reflects albumin rather than true hypocalcemia, since total calcium falls about 0.4 mg/dL for every 1.0 g/dL of albumin lost. The number to trust is ionized calcium, which normally runs 1.1 to 1.4 mmol/L and is measured separately when twitching or weakness appears.