CMP Blood Test: What All 14 Markers Mean

A CMP (comprehensive metabolic panel) is a standard blood test that measures 14 markers across four body systems — glucose, electrolytes, kidney function, and liver/protein levels — in a single blood draw. It is one of the most commonly ordered lab panels, used both as a routine health screen and to monitor ongoing conditions like diabetes, kidney disease, and liver disease.

Normal results vary slightly by laboratory, but the reference ranges below reflect typical adult values used by most major labs.

CMP Reference Ranges — All 14 Markers

What Each Group Measures

Glucose

Glucose is the most sensitive marker to fasting status. A fasting glucose of 100–125 mg/dL is classified as prediabetes; ≥126 mg/dL on two separate draws meets the diagnostic threshold for type 2 diabetes. Glucose below 70 mg/dL indicates hypoglycemia, which in symptomatic patients requires immediate attention.

Electrolytes

Sodium, potassium, chloride, and bicarbonate (CO₂) regulate fluid balance, nerve conduction, and acid-base homeostasis. The most clinically urgent electrolyte abnormality is potassium: levels below 3.0 or above 6.0 mEq/L can cause cardiac arrhythmias and require prompt evaluation regardless of symptoms.

Low sodium (hyponatremia, <135 mEq/L) is common in older adults, in people on certain blood pressure medications, and in states of excess fluid retention. High sodium (hypernatremia, >145 mEq/L) typically reflects dehydration. CO₂ abnormalities suggest metabolic acidosis or alkalosis and often prompt repeat testing alongside a full metabolic workup.

Kidney Function: BUN, Creatinine, and eGFR

These three markers together estimate how well the kidneys filter waste from the blood.

• BUN rises when kidneys are not clearing protein waste efficiently, but also increases with high-protein diets, dehydration, or GI bleeding — so it is interpreted alongside creatinine, not in isolation.
• Creatinine is a more reliable kidney marker because it is less affected by diet. A sustained creatinine rise of more than 0.3 mg/dL from baseline within 48 hours meets the definition of acute kidney injury (AKI).
• eGFR is calculated from creatinine, age, and sex. An eGFR of 60–89 indicates mildly reduced function; 30–59 is moderate chronic kidney disease (CKD); below 15 approaches kidney failure.

Liver and Protein Markers

The liver panel within a CMP has two distinct components: markers of liver cell injury (AST, ALT) and markers of liver synthetic function and bile flow (ALP, bilirubin, albumin, total protein).

• ALT is the most liver-specific enzyme. ALT more than 3× the upper limit of normal warrants investigation. Common causes include nonalcoholic fatty liver disease (NAFLD), alcohol use, viral hepatitis, and statin or other drug effects.
• AST is elevated in liver injury but also in muscle damage, so AST without ALT elevation often points away from the liver toward a musculoskeletal or cardiac cause. An AST:ALT ratio above 2:1 is a classic pattern in alcoholic liver disease.
• ALP elevation in isolation — without elevated AST/ALT — often points to bile duct obstruction or bone disease rather than hepatocellular damage. Normal ALP also varies by age; it is physiologically higher in children and adolescents due to bone growth.
• Total bilirubin above 1.2 mg/dL is jaundice biochemically (visible yellowing of skin/eyes typically appears above 2.5–3.0 mg/dL). Causes range from benign (Gilbert syndrome, a common genetic variant) to serious (bile duct obstruction, hemolysis, acute liver failure).
• Albumin is a measure of what the liver has been manufacturing over the past few weeks, not just right now. Low albumin (<3.5 g/dL) suggests chronic liver disease, malnutrition, or protein-losing conditions such as nephrotic syndrome.

CMP vs. BMP: What's the Difference?

A BMP is typically ordered for a quick electrolyte and kidney check — for example, to monitor a patient on blood pressure medication or IV fluids. A CMP adds the liver panel when there is a reason to assess liver function, screen for hepatitis, evaluate medication effects on the liver, or get a more complete metabolic picture during a routine annual exam.

When Is a CMP Ordered?

• Annual health screening (often bundled with a CBC)
• Monitoring type 2 diabetes (glucose trends, kidney function)
• Chronic kidney disease follow-up (BUN, creatinine, eGFR)
• Liver disease monitoring (AST, ALT, ALP, bilirubin, albumin)
• Before starting or adjusting medications that affect liver or kidneys (statins, NSAIDs, methotrexate, chemotherapy agents)
• Evaluating fatigue, unexplained weight loss, or jaundice
• Checking electrolyte balance in patients on diuretics or with dehydration
• Pre-operative workup

Fasting Requirements

Fasting for 8–12 hours before the draw is preferred. The main reason is glucose — a non-fasting sample will have a predictably higher glucose reading that cannot be compared to the 70–99 mg/dL fasting reference range used to screen for diabetes. All other CMP markers are minimally affected by fasting status. Water is fine to drink; avoid coffee, juice, and food.

If you need a CMP but fasting is difficult (young children, patients with hypoglycemia risk, or logistical constraints), a non-fasting draw is acceptable in most cases — your provider will simply interpret the glucose result in that context.

Getting a CMP Through Mobile Phlebotomy

Speedy Sticks can collect a CMP blood draw at your home or office. If you have an existing lab order, one of our licensed phlebotomists can come to you. If you need a provider to order the test first, we can connect you with a telehealth clinician who can evaluate whether a CMP is appropriate and issue the requisition — eliminating the need for an in-person clinic visit.

A CMP can be drawn at home through mobile phlebotomy — fast the night before, schedule a morning visit, get your 14 markers without leaving home.

Sources and further reading

• Lab Tests Online: Comprehensive Metabolic Panel
• MedlinePlus: Comprehensive Metabolic Panel