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Interpret the panel

Chemistry analytes & differentials

What each chemistry analyte means, the differentials when it rises or falls, and the traps that change the interpretation.

Original educational draft for clinical review. Reference intervals vary by species, age, method and laboratory; interpret every result with the patient and the sample quality in mind.

Liver & cholestasis

ALT (alanine aminotransferase)

Leakage enzyme, the most liver-specific of the common enzymes in dogs and cats.

When it goes up

  • Hepatocellular injury or necrosis (toxins, hypoxia, inflammation, neoplasia)
  • Severe muscle injury (mild contributor)
  • Corticosteroid effect in dogs (mild)
  • Secondary to hyperthyroidism in cats

When it goes down

  • Not clinically meaningful

Worth remembering: Magnitude does not equal prognosis: a cat with hepatic lipidosis can have a near-normal ALT while a dog recovering from acute toxicity may sit at 50x the reference and do well.

AST (aspartate aminotransferase)

Leakage enzyme found in liver AND muscle; never interpret without CK.

When it goes up

  • Hepatocellular injury (with ALT)
  • Skeletal or cardiac muscle injury (with CK)
  • Hemolysis of the sample (artifact)

When it goes down

  • Not clinically meaningful

Worth remembering: AST up with CK up and ALT normal points to muscle, not liver. AST up with ALT up and CK normal points to liver.

ALP (alkaline phosphatase)

Cholestasis enzyme with a short half-life in cats and a steroid-induced form in dogs.

When it goes up

  • Cholestasis (intra- or extrahepatic)
  • Corticosteroids or phenobarbital in dogs (induction)
  • Bone growth in young animals
  • Hyperthyroidism in cats
  • Bone disease (osteoblastic activity)

When it goes down

  • Not clinically meaningful

Worth remembering: Any ALP elevation in a cat matters: feline ALP has a short half-life and low liver stores, so even a doubling is significant. In dogs, a 3x rise from steroids can be benign.

GGT (gamma-glutamyl transferase)

Cholestasis enzyme, more specific for biliary disease than ALP.

When it goes up

  • Biliary tract disease or obstruction
  • Cholangitis or cholangiohepatitis in cats
  • Corticosteroid induction in dogs
  • Colostrum intake in neonates (marked)

When it goes down

  • Not clinically meaningful

Worth remembering: In cats, GGT rising MORE than ALP suggests cholangitis or biliary obstruction; ALP rising more than GGT fits hepatic lipidosis better.

Bilirubin (total)

Function marker, not a leakage enzyme. Split into pre-hepatic, hepatic and post-hepatic causes.

When it goes up

  • Pre-hepatic: hemolysis
  • Hepatic: severe hepatocellular dysfunction
  • Post-hepatic: biliary obstruction, ruptured bile duct
  • Fasting hyperbilirubinemia in horses (benign)

When it goes down

  • Not clinically meaningful

Worth remembering: Anorectic horses commonly run a high bilirubin with a normal liver; feed them and recheck before panicking. Cats essentially never get benign fasting hyperbilirubinemia.

Bile acids

Liver function test: high values mean reduced hepatic uptake or portosystemic shunting.

When it goes up

  • Portosystemic shunt
  • Severe hepatocellular dysfunction
  • Cholestasis
  • Recent meal (physiologic rise, use paired fasted and post-prandial samples)

When it goes down

  • Not clinically meaningful

Worth remembering: High bile acids with low urea, low glucose, low cholesterol and microcytosis in a young dog is the classic shunt pattern. Ammonia is the better single test when a shunt is suspected.

Albumin (as a liver marker)

Made only by the liver; low albumin reflects chronic dysfunction because of its long half-life.

When it goes up

  • Dehydration (with high total protein)

When it goes down

  • Chronic liver failure (decreased production)
  • Protein-losing nephropathy
  • Protein-losing enteropathy
  • Severe blood loss or exudation
  • Negative acute phase response (inflammation)

Worth remembering: Low albumin from liver failure implies roughly three quarters of function is gone and it takes weeks to fall. A patient that lost albumin over days is losing it somewhere, not failing to make it.

Kidney

Urea (BUN)

Filtered by the glomerulus but heavily influenced by non-renal factors.

When it goes up

  • Azotemia: pre-renal (dehydration, poor perfusion), renal, post-renal (obstruction, uroabdomen)
  • High protein meal or GI hemorrhage
  • Corticosteroids, tetracyclines (catabolism)

When it goes down

  • Liver failure or portosystemic shunt (urea cycle)
  • Low protein diet
  • Polyuria or polydipsia of any cause
  • Anabolic steroids

Worth remembering: Urea up with a concentrated urine (USG above 1.030 dog, 1.035 cat) is pre-renal until proven otherwise. Urea up with isosthenuria is renal. Urea down with low cholesterol and low glucose: think shunt.

Creatinine

More kidney-specific than urea; rises only when about three quarters of nephrons are lost.

When it goes up

  • Pre-renal, renal or post-renal azotemia
  • High muscle mass (mild)
  • Severe muscle breakdown (mild)
  • Some cephalosporins interfere with the assay (artifact)

When it goes down

  • Low muscle mass or cachexia
  • Not otherwise meaningful

Worth remembering: Creatinine is insensitive: a dog can lose half its kidney function and stay inside the reference interval. SDMA and urine specific gravity catch disease earlier. Greyhounds and sight hounds run higher; cachectic animals run falsely low.

SDMA (symmetric dimethylarginine)

Earlier marker of falling GFR than creatinine; less affected by muscle mass.

When it goes up

  • Reduced GFR from any cause (pre-renal, renal, post-renal)
  • Rises when roughly 40 percent of function is lost

When it goes down

  • Not clinically meaningful

Worth remembering: SDMA up with creatinine still normal is early kidney disease or a non-renal GFR problem: check hydration and USG before calling it chronic kidney disease.

Phosphorus (renal context)

Excreted by the kidney; retention parallels GFR loss.

When it goes up

  • Renal azotemia (any cause)
  • Young growing animals (physiologic)
  • Hypoparathyroidism
  • Tissue breakdown (tumor lysis, rhabdomyolysis)
  • Vitamin D toxicosis
  • Hemolysis or delayed separation (artifact)

When it goes down

  • Hyperparathyroidism
  • Refeeding syndrome
  • Insulin therapy (shifts into cells)
  • Intestinal phosphate binders

Worth remembering: In a young large-breed dog a high phosphorus with normal creatinine and calcium is usually just growth. In an azotemic cat, phosphorus tracks severity and drives renal secondary hyperparathyroidism.

Proteins

Total protein

Albumin plus globulins; always interpret the two fractions separately.

When it goes up

  • Dehydration (albumin and globulin up together)
  • Chronic inflammation or antigenic stimulation (globulin up)
  • Neoplasia: multiple myeloma, lymphoma (globulin up)

When it goes down

  • Protein loss: kidney, gut, skin, bleeding
  • Liver failure
  • Overhydration
  • Neonates (low until colostrum and maturation)

Worth remembering: High globulin with normal albumin is not dehydration. Dehydration raises both together; a globulin-only rise means antigenic stimulation, and a tall narrow spike on electrophoresis means a monoclonal gammopathy until proven otherwise.

Globulins

Immunoglobulins plus acute phase proteins; calculated as total protein minus albumin.

When it goes up

  • Chronic infection (ehrlichiosis, leishmaniasis, FIP)
  • Immune-mediated disease
  • Lymphoid neoplasia
  • Dehydration (mild, with albumin)

When it goes down

  • Failure of passive transfer in neonates
  • Protein-losing enteropathy
  • Severe combined immunodeficiency (rare)

Worth remembering: A cat with high globulin, low albumin and a low A:G ratio: FIP belongs on the differential list, but so do lymphoma and chronic infection. The ratio is a clue, never a diagnosis.

Glucose & lipids

Glucose

Balanced by insulin, glucagon, cortisol and catecholamines; the sample itself can lie.

When it goes up

  • Diabetes mellitus
  • Stress hyperglycemia (especially cats)
  • Post-prandial
  • Glucocorticoids or progestins
  • Pancreatitis, hyperadrenocorticism, diestrus

When it goes down

  • Insulinoma
  • Sepsis
  • Hypoadrenocorticism
  • Liver failure or shunt
  • Neonates and toy breeds
  • Delayed sample separation (cells consume glucose, artifact)

Worth remembering: A high glucose in a fractious cat with a normal fructosamine is stress, not diabetes. A low glucose in a sample that sat an hour before spinning is the tube, not the patient: use a fluoride oxalate tube or separate promptly.

Fructosamine

Glycated protein reflecting average glucose over the previous one to two weeks.

When it goes up

  • Diabetes mellitus (persistent hyperglycemia)
  • Chronic stress hyperglycemia can raise it mildly

When it goes down

  • Hypoalbuminemia or protein loss (falsely low)
  • Hyperthyroidism in cats (faster protein turnover)
  • Prolonged hypoglycemia

Worth remembering: Fructosamine rides on albumin: a hypoalbuminemic diabetic can show a deceptively normal fructosamine. In cats, check the thyroid before trusting it.

Cholesterol

Influenced by diet, hormones, liver function and protein loss.

When it goes up

  • Post-prandial
  • Hypothyroidism
  • Hyperadrenocorticism
  • Cholestasis
  • Nephrotic syndrome
  • Diabetes mellitus
  • Inherited hyperlipidemia (Miniature Schnauzer, Briard)

When it goes down

  • Portosystemic shunt or liver failure
  • Protein-losing enteropathy
  • Malabsorption or starvation

Worth remembering: Low cholesterol with low urea and low glucose is the liver function triad; low cholesterol with low albumin and low globulin points at the gut. Same analyte, opposite direction, completely different organs.

Triglycerides

The cause of a lipemic sample; interfere with many other assays.

When it goes up

  • Post-prandial (most common)
  • Inherited hyperlipidemia
  • Hypothyroidism
  • Diabetes mellitus
  • Hyperadrenocorticism
  • Pancreatitis (cause or effect)
  • Nephrotic syndrome

When it goes down

  • Not clinically meaningful

Worth remembering: Lipemia is the great confounder: it falsely raises phosphorus, bilirubin and many chemistry results and can falsely lower others. Fast the patient 12 hours and repeat before believing a weird panel.

Electrolytes & minerals

Sodium

Follows water: always ask what the water balance is doing.

When it goes up

  • Water loss exceeding salt loss: water deprivation, diabetes insipidus, heatstroke
  • Salt gain: hypertonic saline, salt poisoning
  • Hyperaldosteronism (mild)

When it goes down

  • Hypoadrenocorticism
  • GI loss with water replacement
  • Diuretics
  • Third-space loss (effusions, uroabdomen)
  • Severe hyperglycemia (dilutional)
  • Psychogenic polydipsia or SIADH

Worth remembering: Hyponatremia with hyperkalemia and a Na:K ratio below 24 is the classic Addisonian pattern, but whipworms, GI disease and effusions can mimic it. Correct sodium slowly: rapid correction risks myelinolysis.

Potassium

Mostly intracellular; the ECG matters more than the number.

When it goes up

  • Hypoadrenocorticism
  • Urethral obstruction or uroabdomen
  • Acute kidney injury or oliguria
  • Acidosis (shift out of cells)
  • Tissue breakdown or reperfusion
  • Hemolysis in Akitas and similar breeds (artifact)

When it goes down

  • GI loss (vomiting, diarrhea)
  • Chronic kidney disease in cats
  • Diuretics
  • Insulin or glucose therapy (shift into cells)
  • Alkalosis
  • Anorexia

Worth remembering: Potassium-containing fluids are not inherently dangerous: the rate is what matters. Treat the ECG first (calcium gluconate for cardiotoxicity), then shift potassium into cells (insulin with dextrose), then remove the cause.

Chloride

Interpret as corrected chloride relative to sodium.

When it goes up

  • Diarrhea (loss of bicarbonate-rich fluid)
  • Renal tubular acidosis
  • Normal saline administration
  • Acetazolamide

When it goes down

  • Vomiting of stomach contents (loss of HCl)
  • Loop or thiazide diuretics
  • Hyperadrenocorticism
  • Bromide in the sample (falsely raises measured chloride on some analyzers)

Worth remembering: A vomiting dog with low corrected chloride, low potassium and a metabolic alkalosis is the pyloric or duodenal obstruction pattern. Corrected chloride, not the raw number, tells the story.

Calcium (total)

About half is bound to albumin; correct for albumin in dogs, measure ionized calcium in cats.

When it goes up

  • Malignancy (lymphoma, anal sac adenocarcinoma)
  • Primary hyperparathyroidism
  • Vitamin D toxicosis (cholecalciferol rodenticide, plants)
  • Chronic kidney disease (variable)
  • Hypoadrenocorticism
  • Lipemia or young growing animals (mild)

When it goes down

  • Hypoalbuminemia (most common, correction fixes it)
  • Eclampsia
  • Ethylene glycol toxicosis
  • Acute pancreatitis
  • Hypoparathyroidism
  • Citrate transfusion or EDTA contamination (artifact)

Worth remembering: Always correct for albumin before calling a dog hyper- or hypocalcemic, and remember the correction formula is unreliable in cats: order ionized calcium there. A dog with high calcium and low phosphorus: think malignancy first.

Bicarbonate (TCO2)

The metabolic arm of acid-base; interpret with chloride, potassium and the clinical picture.

When it goes up

  • Metabolic alkalosis: vomiting of gastric contents, diuretics, hyperadrenocorticism
  • Compensation for chronic respiratory acidosis

When it goes down

  • Metabolic acidosis: kidney failure, diarrhea, diabetic ketoacidosis, lactic acidosis, toxins (ethylene glycol)
  • Compensation for chronic respiratory alkalosis
  • Sample exposed to air (artifact, mild)

Worth remembering: A low bicarbonate with a high anion gap means an added acid (uremic acids, lactate, ketones, toxin metabolites). A low bicarbonate with a normal gap means bicarbonate was lost (diarrhea, renal tubular acidosis).

Muscle & pancreas

CK (creatine kinase)

Muscle leakage enzyme with a very short half-life.

When it goes up

  • Skeletal muscle injury, myositis, ischemia
  • Seizures, recumbency, restraint or IM injection
  • Exercise (transient)
  • Malignant hyperthermia

When it goes down

  • Not clinically meaningful

Worth remembering: CK has a half-life of a few hours: a normal CK does not exclude muscle disease that happened days ago, and a huge CK after a seizure can normalize within a day. Recheck rather than over-interpret.

Lipase & amylase

Traditional pancreatic enzymes; neither is specific for pancreatitis.

When it goes up

  • Pancreatitis (variable sensitivity)
  • Kidney disease (reduced clearance)
  • GI disease
  • Corticosteroids (lipase, dogs)
  • Dehydration

When it goes down

  • Not clinically meaningful

Worth remembering: A three-fold lipase rise in a vomiting dog is suggestive but not proof of pancreatitis: kidney disease and GI disease do the same. Species-specific pancreatic lipase tests (cPLI, fPLI) are far more reliable.

Pancreatic lipase (cPLI / fPLI)

Species-specific pancreatic lipase immunoreactivity; the best blood test for pancreatitis.

When it goes up

  • Pancreatitis
  • Kidney disease (mild, reduced clearance)
  • Recent meal (mild)

When it goes down

  • Not clinically meaningful

Worth remembering: Cats with pancreatitis often show no vomiting and a normal ultrasound; a high fPLI in a cat with anorexia and weight loss deserves to be believed. In dogs, very high cPLI with classic signs is about as close to a blood-test diagnosis as pancreatitis gets.