- 01BMP is 8 tests, CMP is 14
The BMP covers kidneys, electrolytes and glucose. The CMP adds albumin, total protein, ALP, ALT, AST and bilirubin for the liver and proteins.
- 02BUN alone versus BUN with creatinine
A high BUN with a normal creatinine usually means fluid, protein or gut bleeding. When creatinine is high too, the kidneys or the blood flow to them are in question, and the ratio gives a rough hint at which.
- 03Read by group and by trend
With 14 tests, simple probability says roughly half of healthy people will get at least one flag. A pattern across related tests, or a change from your own last result, says more than one flag.
A metabolic panel is one tube of blood run for 8 tests (the basic metabolic panel, or BMP) or 14 tests (the comprehensive metabolic panel, or CMP). 1 2 The 14 numbers make sense once you sort them into four groups: kidneys, electrolytes and acid-base, blood sugar, and liver and proteins. Each group answers its own question, and the most useful readings come from comparing numbers inside a group and across groups.
The panel is sometimes called a chem 7 (the BMP) or a chem 14 (the CMP). Both measure substances dissolved in the liquid part of your blood, so they say nothing about your blood cells. Red cells, white cells and platelets are on a different test, the complete blood count, which is often ordered at the same visit.
What is the difference between a BMP and a CMP?
The BMP covers the kidneys, the main electrolytes and blood sugar. The CMP adds a liver and protein block. Some labs also print values they calculate from the measured ones, such as eGFR, the anion gap, the BUN to creatinine ratio, globulin and the albumin to globulin ratio, so your report may show more than 14 lines.
| Test | Group | On a BMP | On a CMP | Typical adult range (labs vary) |
|---|---|---|---|---|
| Glucose | Blood sugar | Yes | Yes | 70 to 99 mg/dL fasting |
| Calcium | Electrolytes and minerals | Yes | Yes | 8.5 to 10.2 mg/dL |
| Sodium | Electrolytes | Yes | Yes | 135 to 145 mmol/L |
| Potassium | Electrolytes | Yes | Yes | 3.5 to 5.0 mmol/L |
| CO2 (bicarbonate) | Acid-base | Yes | Yes | 22 to 29 mmol/L |
| Chloride | Electrolytes | Yes | Yes | 96 to 106 mmol/L |
| BUN | Kidneys | Yes | Yes | 7 to 20 mg/dL |
| Creatinine | Kidneys | Yes | Yes | About 0.6 to 1.3 mg/dL (lower in women) |
| Albumin | Liver and proteins | No | Yes | 3.5 to 5.0 g/dL |
| Total protein | Liver and proteins | No | Yes | 6.0 to 8.3 g/dL |
| ALP | Liver and bone | No | Yes | About 40 to 130 U/L |
| ALT | Liver | No | Yes | Lab upper limits often 40 to 55 U/L |
| AST | Liver and muscle | No | Yes | Lab upper limits often 35 to 45 U/L |
| Bilirubin, total | Liver | No | Yes | About 0.1 to 1.2 mg/dL |
Use the range printed on your own report, because ranges shift with the lab's equipment, your age and sex, and pregnancy. Glucose, BUN, creatinine and calcium are shown here in US units (mg/dL); many countries report them in mmol/L or µmol/L, which changes every number on the page. Blood-test units explained covers the conversions.
How to read a metabolic panel in four groups
- 1Kidneys first: BUN, creatinine, eGFRThese three tell you how well the kidneys are clearing waste, and they set the frame for everything else, because the kidneys also control sodium, potassium and acid-base balance.
- 2Electrolytes and acid-base: sodium, potassium, chloride, CO2, calciumThese describe fluid balance and the blood's acid level. Potassium carries the most urgent flags on the whole panel.
- 3Blood sugar: glucoseA single glucose value is only interpretable once you know whether you had eaten.
- 4Liver and proteins (CMP only): ALT, AST, ALP, bilirubin, albumin, total proteinThe pattern matters more than any one value: enzymes from liver cells (ALT, AST) versus the bile-flow enzyme (ALP), and what the liver makes (albumin).
BUN, creatinine and eGFR: how to read them together
BUN (blood urea nitrogen) is a waste product of protein breakdown made in the liver. Creatinine is a waste product of muscle. The kidneys clear both, but BUN also rises and falls with hydration, protein intake and bleeding in the gut, while creatinine tracks kidney filtration more closely. 3 That difference is why the two are read as a pair, and why many reports print the BUN to creatinine ratio, usually around 10:1 to 20:1.
| Pattern | What it usually points to | What else to look at |
|---|---|---|
| BUN high, creatinine normal | Dehydration, a high-protein diet, steroid medicines, or bleeding in the stomach or upper gut 3 | Sodium and albumin (often high-normal when dry); black or tarry stools are a red flag for bleeding |
| BUN and creatinine both high, ratio above about 20 | Often reduced blood flow to the kidneys, such as dehydration, heart failure or blood loss | Repeat after rehydration if dehydration is likely; blood pressure and medicines |
| BUN and creatinine both high, ratio 10 to 20 | More often a problem in the kidney itself, short-term or long-term; the ratio is a rough hint, not a diagnosis | eGFR, potassium, CO2 and a urine albumin test |
| Creatinine high, BUN normal | Large muscle mass, a big meat meal, creatine supplements, or medicines that block creatinine secretion | eGFR trend; a cystatin C test can help settle it |
| BUN low | Low protein intake, pregnancy, a lot of fluid, or less often reduced liver function | Albumin and the liver tests on a CMP |
Creatinine depends on how much muscle you have, so a muscular man and a small older woman can have the same kidney function and very different creatinine values. Creatine supplements and a large serving of cooked meat in the hours before the draw can lift creatinine without any change in the kidneys.
Estimate your kidney filtration (eGFR)
From your creatinine. Nothing leaves your browser.
eGFR is calculated from creatinine, age and sex, and estimates how many milliliters of blood the kidneys filter per minute. The current US equation (CKD-EPI 2021) no longer uses race, and an equation that adds cystatin C to creatinine is more accurate than creatinine alone. 5 KDIGO, the international kidney guideline group, defines chronic kidney disease as an eGFR below 60, or signs of kidney damage such as albumin in the urine, lasting more than 3 months. 4 One low eGFR is a reason to repeat the test before anyone names a diagnosis; the kidney function guide and the chronic kidney disease page go further.
Sodium, potassium, chloride and CO2
Sodium mostly reflects the balance of water in the body, more than how much salt you eat. Potassium matters for the heart rhythm, which is why it has the tightest range and the most urgent flags. Chloride usually moves with sodium. CO2 on a metabolic panel is bicarbonate, the blood's main buffer against acid, so it reads the blood's acid balance rather than the gas in your breath. The electrolytes guide covers each one in depth.
| Flag | Common reasons | Read it beside |
|---|---|---|
| Sodium low | Extra water held back (some diuretics, antidepressants, heart, liver or kidney disease), heavy sweating with plain water replacement, very high glucose | Glucose (very high sugar draws water into the blood and dilutes sodium), symptoms such as confusion or headache |
| Sodium high | Not enough water, often in older adults or with fever or diarrhea | BUN (often up too) |
| Potassium high | A burst sample (hemolysis), kidney disease, some blood pressure medicines | Creatinine and eGFR; the lab comment for hemolysis |
| Potassium low | Diuretics, vomiting, diarrhea | CO2 (often high after vomiting), magnesium |
| CO2 low | Acid build-up (kidney disease, diarrhea, diabetic ketoacidosis) or fast breathing | Anion gap, glucose, creatinine |
| CO2 high | Vomiting, diuretics, long-term lung disease | Chloride and potassium (often low) |
When CO2 is low, the anion gap helps sort the cause. It is sodium minus the sum of chloride and CO2, and it estimates acids the panel does not measure directly. A raised gap points toward acids such as ketones or lactate; a normal gap with low CO2 points more toward bicarbonate lost through the gut or kidneys. The anion gap calculator works it out from your report.
Calcium
About 40% of the calcium in blood rides on albumin, so a low albumin pulls total calcium down without any real shortage. A corrected calcium adjusts for that, and an ionized calcium test measures the free fraction directly. A high calcium on a routine panel is most often from the parathyroid glands; the hyperparathyroidism page explains how a parathyroid hormone (PTH) test is read beside it.
What does the glucose on a metabolic panel mean?
Fasting glucose, an example resultmg/dL
The American Diabetes Association's fasting cutoffs assume at least 8 hours with no food or caloric drinks. 6 A glucose of 130 two hours after lunch is unremarkable, while the same number after an overnight fast is in the diabetes range, so check whether the sample was fasting before reading it. Diabetes is diagnosed on two abnormal results, or on one random glucose of 200 mg/dL or more with classic symptoms such as heavy thirst and frequent urination. 6 Hemoglobin A1c averages the last 2 to 3 months and is often added when glucose looks high. The blood sugar guide, prediabetes and type 2 diabetes pages take it from there.
Liver numbers on a CMP: ALT, AST, ALP and bilirubin
The six liver and protein tests are often called liver function tests, but only albumin and bilirubin reflect what the liver does. ALT and AST are enzymes that leak out of damaged liver cells, and ALP rises when bile flow is slowed or bone is turning over quickly. The American College of Gastroenterology guideline makes the point directly:
These tests should be termed liver chemistries or liver tests.Kwo PY, et al. ACG Clinical Guideline: Evaluation of Abnormal Liver Chemistries. Am J Gastroenterol 2017 7
| Pattern | What it usually means | Read it beside |
|---|---|---|
| ALT and AST up more than ALP | Liver cell injury (hepatocellular pattern): fatty liver, alcohol, medicines, viral hepatitis 7 | AST to ALT ratio; the fatty liver page |
| ALP up more than ALT and AST | Slowed bile flow (cholestatic pattern) 7 | GGT: a high GGT says the ALP is from the liver, a normal GGT points to bone |
| ALP up alone in a teenager, after a fracture or in pregnancy | Bone growth or healing, or the placenta | Age and context; usually no liver concern |
| AST up alone, ALT normal | Muscle: hard exercise in the days before the test, or a muscle injury | Creatine kinase (CK) if it was checked |
| Bilirubin mildly up alone, other liver tests normal | Often Gilbert syndrome, a harmless inherited pattern that rises with fasting or illness | Direct and indirect bilirubin split |
Lab upper limits for ALT are often 40 U/L or higher, but the ACG guideline puts a healthy ALT at 29 to 33 U/L for men and 19 to 25 U/L for women, and says values above that should be assessed. 7 So an ALT of 38 can carry no flag on your report and still be worth a mention. The liver enzymes guide covers the patterns in full.
Albumin and total protein
Albumin is made by the liver and is the main protein in blood. It falls with long-standing liver disease, protein lost through the kidneys or gut, poor nutrition, and acute or chronic inflammation, and it rises a little when you are dehydrated. Total protein is albumin plus everything else, mostly antibodies. Subtracting one from the other gives globulin. A high total protein with a high globulin and a low albumin to globulin ratio can come from chronic infection or inflammation and, less often, from a blood cancer called myeloma, so a persistent gap is something to ask about rather than ignore.
How to read the groups together
Several common situations leave fingerprints across more than one group. Spotting the pattern is what turns four or five flags into one explanation.
| Situation | Kidney group | Electrolytes and acid-base | Glucose | Liver and proteins |
|---|---|---|---|---|
| Dehydration | BUN up, ratio above 20, creatinine normal or slightly up | Sodium high-normal or high | Unchanged | Albumin and total protein high-normal |
| Repeated vomiting | BUN may rise | CO2 high, chloride and potassium low | Unchanged | Unchanged |
| Reduced kidney function | Creatinine and BUN up, eGFR down | Potassium up, CO2 down | Unchanged | Albumin may fall if protein leaks into urine |
| Very high blood sugar | BUN and creatinine may rise from fluid loss | Sodium reads low; CO2 low and anion gap high if ketones build up | High | Unchanged |
| Long-standing liver disease | BUN low | Sodium may be low | Can run low | Albumin low, bilirubin up; ALT and AST may be only mildly raised |
Do you need to fast for a CMP or BMP?
MedlinePlus says you may need to fast for 8 hours before a BMP 2 and for several hours before a CMP. 1 Fasting mainly protects the glucose result; the other lines move little after a normal meal, although a large protein meal can nudge BUN and creatinine up. Plain water is usually allowed and makes the draw easier. Whether to fast is the ordering clinician's call, often based on whether a lipid panel is being drawn at the same time, and you should never skip a prescribed medicine to prepare for a panel without asking the prescriber first.
- Hard exercise in the 1 to 3 days before the test can raise AST, creatinine and CK.
- A sample that sits too long before processing, or that hemolyzes, can raise potassium and AST and lower glucose.
- Being dehydrated concentrates the blood and lifts BUN, sodium, albumin and total protein.
- Creatine supplements and a big meat meal can raise creatinine; a high-protein day can raise BUN.
- Pregnancy lowers BUN, creatinine and albumin and raises ALP, so non-pregnant ranges misread a pregnant panel.
Why one flag on a metabolic panel is common
That arithmetic is why a single result slightly outside the range, with every related number normal, is usually repeated or watched rather than chased. The reference ranges guide explains where the ranges come from. The opposite also holds: a number inside the range can still be a change for you, which is why comparing with your own earlier results is often more useful than the flag. The guide to trends shows how to do that, and how to read any lab result gives the general method.
Link · MedlinePlus, US National Library of MedicineComprehensive Metabolic Panel (CMP)The NLM's plain-language reference on what the 14 CMP tests are, why the panel is ordered and how to prepare.medlineplus.gov
Citations
- MedlinePlus, US National Library of Medicine. Comprehensive Metabolic Panel (CMP). Lab test information.
- MedlinePlus, US National Library of Medicine. Basic Metabolic Panel (BMP). Lab test information.
- Hosten AO. BUN and Creatinine. In: Walker HK, Hall WD, Hurst JW, eds. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd ed. Butterworths; 1990. Chapter 193.
- Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int. 2024;105(4S):S117-S314.
- Inker LA, et al. New creatinine- and cystatin C-based equations to estimate GFR without race. N Engl J Med. 2021;385(19):1737-1749.
- American Diabetes Association Professional Practice Committee. 2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes 2025. Diabetes Care. 2025;48(Suppl 1):S27-S49.
- Kwo PY, Cohen SM, Lim JK. ACG Clinical Guideline: Evaluation of Abnormal Liver Chemistries. Am J Gastroenterol. 2017;112(1):18-35.
- Shah A, Dohner J, Cheng K, Garcia M, Kost GJ. Visualization of critical limits and critical values facilitates interpretation. Diagnostics (Basel). 2025;15(5):604.
Educational context only, not medical advice or a diagnosis. Always discuss your results with a clinician.
