Along with a blood count and cholesterol test, most routine checkups include a metabolic panel — a long list of abbreviations such as BUN, eGFR, ALT and K. When one of them is flagged, the report rarely explains what it means.
The basic metabolic panel (BMP) and comprehensive metabolic panel (CMP) give a quick overview of kidney function, liver function, blood sugar and the balance of electrolytes in your blood. This guide explains the main values and why they sometimes fall slightly outside the reference range.
Key Takeaways
- The BMP covers glucose, electrolytes and kidney function; the CMP adds liver tests and proteins.
- eGFR estimates how well your kidneys filter blood; a value persistently below 60 for three months or more may indicate chronic kidney disease.
- Mildly raised liver enzymes (ALT and AST) are common and can be caused by fatty liver, alcohol, medications, recent exercise or viral illness.
- Dehydration, recent heavy exercise and some medications commonly affect metabolic panel results.
This article is general information. Always compare results with your lab’s own reference ranges and discuss them with your clinician.
The basic metabolic panel
Glucose. Blood sugar at the time of the test. Whether you fasted makes a big difference. A fasting value under 100 mg/dL is generally considered normal.
Sodium (Na). Usually about 135 to 145 mmol/L. Sodium balance is controlled mainly by water balance. Low sodium can occur with some medications (such as certain diuretics and antidepressants), heart, liver or kidney conditions, or drinking very large amounts of water. High sodium most commonly reflects dehydration.
Potassium (K). Usually about 3.5 to 5.0 mmol/L. Potassium is important for heart and muscle function. Low potassium can occur with diuretics, vomiting or diarrhea. High potassium can occur with kidney disease and some blood pressure medications. Falsely high results can happen if blood cells break during collection.
Chloride and bicarbonate (CO2). Help assess acid-base balance and hydration.
Blood urea nitrogen (BUN). A waste product from protein breakdown, filtered by the kidneys. It can rise with dehydration, high-protein diets, some bleeding in the digestive tract, or reduced kidney function.
Creatinine. A waste product from muscle metabolism, filtered by the kidneys. Levels depend partly on muscle mass, so muscular people may have higher values.
eGFR (estimated glomerular filtration rate). An estimate of how well the kidneys filter blood, calculated from creatinine, age and sex. Values of 90 or above are generally considered normal; values between 60 and 89 may be normal for older adults or may indicate mildly reduced function. Values persistently below 60 for three months or more may indicate chronic kidney disease.
Calcium. Important for bones, nerves and muscles. Abnormal levels can relate to parathyroid glands, vitamin D, kidney function or some medications.
The extra tests in a comprehensive panel
Albumin and total protein. Proteins produced mainly by the liver. Low albumin can reflect liver disease, kidney protein loss, inflammation or poor nutrition.
ALT (alanine aminotransferase) and AST (aspartate aminotransferase). Enzymes found in liver cells, released into the blood when liver cells are irritated or damaged. AST is also found in muscle.
Alkaline phosphatase (ALP). Found in the liver, bile ducts and bone. It can rise with bile duct problems, bone growth or bone disease. It is naturally higher in growing children and teenagers.
Bilirubin. A breakdown product of red blood cells processed by the liver. A mildly high bilirubin with otherwise normal liver tests is often due to Gilbert’s syndrome, a common and harmless inherited condition.
Common reasons for mildly abnormal results
Dehydration. Can raise BUN, creatinine, sodium and albumin.
Recent intense exercise. Can raise creatinine and AST because of muscle breakdown. Avoid heavy workouts in the day or two before a blood test if possible.
Medications. Many drugs affect the metabolic panel, including diuretics, some blood pressure medications, statins and some pain relievers.
Fatty liver. Metabolic dysfunction-associated steatotic liver disease, often linked to excess weight, diabetes and high triglycerides, is a very common cause of mildly raised ALT.
Alcohol. Can raise liver enzymes.
Supplements. Some herbal and bodybuilding supplements can affect liver tests.
When results need follow-up
Your clinician will consider:
- How far outside the range the value is
- Whether it is a new change
- Whether several related values are abnormal together
- Your symptoms, medications and medical history
A single mildly abnormal value is often repeated. Persistent abnormalities may lead to further tests, such as urine tests for kidney function or ultrasound for the liver.
Questions to ask your clinician
- Is this value meaningfully abnormal, or within normal variation for me?
- Could my medications, supplements, hydration or recent exercise explain it?
- How does it compare with my previous results?
- Do I need a repeat test or additional tests?
- Is there anything I should change before the next test?
Frequently Asked Questions
Does a low eGFR always mean kidney disease? Not necessarily. eGFR can be lower with dehydration or temporary illness, and it naturally declines with age. Chronic kidney disease is diagnosed when reduced function or kidney damage persists for at least three months.
Can drinking water before a blood test help? Staying normally hydrated helps ensure results reflect your usual state. Follow fasting instructions if given.
Are slightly high liver enzymes dangerous? Mild elevations are common and often reversible, but persistent elevations should be investigated.
Why is my creatinine high when I feel fine? Higher muscle mass, high protein intake, dehydration or recent exercise can raise creatinine.
The bottom line
The metabolic panel is a broad screening tool. Mild abnormalities are common and often explained by hydration, exercise or medications. Persistent or significant changes deserve a follow-up conversation.