CMP vs BMP: What's the Difference, and Which Metabolic Panel Do You Need?

Both panels are run from a single tube of blood on the same chemistry analyzer, and the first eight results are identical. The basic metabolic panel stops there: glucose, calcium, four electrolytes (sodium, potassium, chloride, carbon dioxide) and two kidney markers (BUN and creatinine). The comprehensive metabolic panel adds six more: two proteins (albumin and total protein) and four liver values (ALT, AST, alkaline phosphatase and total bilirubin). Eight versus fourteen is the whole difference.

In practice that extra block is the liver. If the question is "how are the kidneys, sugar and salts?", a BMP answers it. If the question includes "and how is the liver?", it has to be a CMP. Because most annual physicals, medication checks and general work-ups want the liver included, the CMP is the more commonly ordered of the two and the one included in most wellness panels.

Neither panel includes a blood count, cholesterol, thyroid function or hemoglobin A1c; those are separate tests that are often drawn at the same visit.

Value	BMP	CMP	Reference range (adults)	What it tells you
Glucose	Yes	Yes	70.0 – 99.0 mg/dL	Blood sugar at the moment of the draw; fasting values of 100–125 mg/dL are prediabetes range, 126+ on two occasions diabetes
Calcium	Yes	Yes	8.60 – 10.3 mg/dL	Bone, nerve and muscle signaling; abnormal values point to parathyroid, vitamin D or kidney problems
Sodium	Yes	Yes	135 – 145 mmol/L	Water balance; low with over-hydration, some medications and illness, high with dehydration
Potassium	Yes	Yes	3.50 – 5.00 mmol/L	Heart rhythm and muscle function; sensitive to kidney function and medications such as diuretics and ACE inhibitors
Chloride	Yes	Yes	98.0 – 107 mmol/L	Tracks sodium; helps interpret acid–base balance
Carbon dioxide (bicarbonate)	Yes	Yes	see your report	Acid–base balance; low in acidosis, high in alkalosis or lung disease
BUN (blood urea nitrogen)	Yes	Yes	7.00 – 20.0 mg/dL	Kidney filtration and hydration; rises with dehydration, high protein intake and kidney impairment
Creatinine	Yes	Yes	Men 0.740 – 1.35 mg/dL; Women 0.590 – 1.04 mg/dL	The main kidney filtration marker; used to calculate eGFR
Albumin	—	Yes	3.50 – 5.00 g/dL	The main blood protein, made by the liver; low with liver disease, kidney protein loss, inflammation or malnutrition
Total protein	—	Yes	6.30 – 8.30 g/dL	Albumin plus globulins; abnormal values prompt a look at liver, kidney and immune proteins
ALT	—	Yes	Men 7.00 – 55.0 U/L; Women 7.00 – 45.0 U/L	Liver enzyme most specific for liver cell injury — fatty liver, alcohol, medications, hepatitis
AST	—	Yes	Men 8.00 – 48.0 U/L; Women 8.00 – 43.0 U/L	Liver enzyme also found in muscle and heart; read with ALT
Alkaline phosphatase	—	Yes	40.0 – 129 U/L	Bile duct and bone enzyme; high with bile flow problems, bone turnover, growth and pregnancy
Bilirubin	—	Yes	0.100 – 1.20 mg/dL	Breakdown product of red cells cleared by the liver; high with liver disease, bile obstruction or rapid red cell destruction

Most reports also show an eGFR (reference 60.0 – 120 mL/min/1.73m2), calculated from creatinine, age and sex, and some add an anion gap or a BUN/creatinine ratio. Ranges shown are the reviewed adult reference bands used across TestWell; your report's printed range is the one to interpret against.

The BMP is the panel of acute and focused questions. Emergency departments and hospitals run it to check electrolytes, kidney function and glucose quickly and repeatedly. Clinicians order it to monitor people on diuretics, ACE inhibitors, ARBs, lithium or other drugs that move potassium, sodium or creatinine; to follow chronic kidney disease between fuller checks; to look at hydration and electrolytes during vomiting, diarrhea or illness; and to check blood sugar when the liver is not in question.

Choose the BMP yourself when a recent CMP already showed normal liver values and you only need to recheck the kidneys, sugar or electrolytes, or when a medication label tells you to monitor potassium or creatinine specifically.

The CMP is the default for anything broad. Annual blood work and physicals use it because the six added values catch fatty liver disease, alcohol-related liver injury, hepatitis and bile-duct problems that produce no symptoms until late. It is the panel for monitoring medications that can stress the liver — statins, methotrexate, isotretinoin, many antifungals and anti-seizure drugs, GLP-1 medications and testosterone therapy — and for anyone who drinks regularly, has been told they have a fatty liver, or is checking a baseline before starting a new therapy or a supplement regimen.

The protein values add their own information: a low albumin can be the first laboratory sign of liver disease, kidney protein loss or chronic inflammation, and total protein helps flag immune-protein disorders. If you are unsure which panel you want, the CMP is the safer default, and through TestWell it costs $2.00 more than the BMP ($22.99 vs $20.99).

Fasting matters for one line on either panel: glucose. The reference range for glucose is a fasting range, and a value drawn after a meal cannot be compared to it. Most labs and clinicians therefore ask for an 8–12 hour fast before either panel — water is fine, and take usual medications unless told otherwise. A non-fasting panel is still useful for the kidneys, electrolytes and liver; the glucose is simply read as a random value, and a fasting glucose or hemoglobin A1c is ordered if blood sugar is the question.

Two other preparation points: intense exercise in the day before can raise AST (and creatinine slightly) because both are also released from muscle, and dehydration lifts BUN, creatinine and sodium. A rested, hydrated morning draw gives the cleanest baseline.

Start with the kidneys: creatinine and eGFR together. An eGFR of 60 or above with a normal creatinine is normal kidney filtration; below 60 for more than three months defines chronic kidney disease; a single low value after dehydration or heavy exercise is repeated. BUN rises with dehydration and high protein intake as well as kidney impairment, so a high BUN with a normal creatinine usually means the former.

Then glucose: a fasting value of 70.0 – 99.0 mg/dL is normal, 100–125 mg/dL is the prediabetes range and 126 mg/dL or higher on two occasions meets the diabetes threshold — an A1c confirms either way. Electrolytes outside range are interpreted with your medications and symptoms; potassium in particular is rechecked promptly when abnormal because both high and low values affect heart rhythm.

On the CMP, ALT and AST are read as a pair. Mild elevations (under about twice the upper limit) are most commonly fatty liver, alcohol or a medication and are usually repeated after addressing the likely cause; higher or persistent elevations lead to hepatitis testing, imaging and a fuller liver work-up. Alkaline phosphatase and bilirubin together point toward the bile ducts; an isolated mildly high bilirubin in a healthy person is often the benign inherited variant Gilbert syndrome. A low albumin is followed up with the liver, kidney and inflammation markers. The liver function tests guide goes through these patterns in more depth.

As with any panel, a single mildly abnormal value is frequently transient. Markedly abnormal potassium, sodium, glucose or creatinine, or abnormal liver values with jaundice, abdominal pain or dark urine, should be seen promptly rather than watched.

You can order a CMP or BMP online through TestWell — a licensed physician reviews the order, you fast overnight and visit a nearby Quest or Labcorp patient service center, and results appear in your portal, typically within 1–3 business days — or through your own clinician. Both panels are also included in the wellness panels that add a blood count, lipids and thyroid function from the same draw, which is the usual way to get a full annual baseline in one visit.