The basic metabolic panel — usually shortened to BMP — is a group of eight blood tests that measure key chemicals controlling kidney function, fluid and electrolyte balance, and blood sugar. It is one of the most commonly ordered blood test panels in medicine and is a routine part of evaluating people who are unwell, monitoring people with chronic conditions, and screening healthy adults during check-ups.
The BMP gives doctors a quick snapshot of how the kidneys are filtering waste, how the body is balancing salts and fluids, and how blood sugar is being controlled. This article explains what each component measures, why the test is done, and what abnormal results may mean.
The reference range that applies to your result is the one printed on your laboratory report, not the typical ranges shown here. Reference ranges vary between laboratories based on the equipment used, the population tested, and individual factors such as age, sex, and pregnancy status. Always compare your result to the reference range printed on your own report, and discuss any abnormal result with your doctor.
What is a basic metabolic panel?
A basic metabolic panel is a group of eight measurements performed together on a single blood sample:
- Sodium (Na) — an electrolyte that controls fluid balance
- Potassium (K) — an electrolyte that controls heart and muscle function
- Chloride (Cl) — an electrolyte that helps maintain fluid balance and acid-base balance
- Bicarbonate (CO2 or HCO3) — a measure of acid-base balance in the blood
- Blood urea nitrogen (BUN) — a waste product cleared by the kidneys
- Creatinine — a waste product cleared by the kidneys, the most useful single measure of kidney function
- Glucose — blood sugar
- Calcium — a mineral important for bones, nerves, muscles, and the heart
The BMP is sometimes called a “chem 7” or “chem 8” — the chem 7 includes everything except calcium, while the chem 8 includes all eight. When the panel is expanded to include liver-related measurements, it becomes a comprehensive metabolic panel (CMP).
Why is a BMP done?
The BMP is a versatile screening and monitoring test used in many situations:
- To investigate symptoms. Confusion, weakness, fatigue, nausea, irregular heartbeat, frequent urination, and many other symptoms can be caused by problems with electrolytes, kidney function, or blood sugar.
- To check kidney function. The BMP includes the most commonly used measures of kidney function and is the standard method for screening for and monitoring chronic kidney disease.
- To monitor known conditions. People with diabetes, kidney disease, heart failure, high blood pressure, and other chronic conditions often have BMPs done regularly.
- To monitor medications. Many medications — including diuretics (“water pills”), ACE inhibitors, certain antibiotics, lithium, and chemotherapy — can affect kidney function or electrolytes.
- Before surgery. A BMP is often part of routine pre-operative testing.
- In emergency settings. The BMP is one of the most commonly ordered tests in the emergency department because it can quickly identify dangerous electrolyte imbalances and acute kidney problems.
- For routine screening. Many doctors include a BMP as part of routine annual health check-ups for adults.
How is the test performed?
A BMP is performed on a small sample of blood, usually drawn from a vein in the arm. The blood is collected into a tube and analyzed by automated laboratory equipment. Results are usually available within a few hours.
The glucose component of the BMP is affected by recent food intake, so the test may be ordered as a fasting BMP, requiring eight to twelve hours without food beforehand, or as a non-fasting test. Your doctor will tell you which to do. The other seven components do not require fasting.
Components of the basic metabolic panel
Sodium (Na)
Sodium is the body’s most important electrolyte for controlling fluid balance — the amount of water in and around cells, in the blood, and in tissues. It also plays a key role in maintaining acid-base balance and supports nerve and muscle function.
A typical reference range for adults is 135–145 milliequivalents per litre (mEq/L) or millimoles per litre (mmol/L) — these units are equivalent for sodium.
Causes of low sodium (hyponatremia):
- Drinking very large amounts of water (water intoxication)
- Diuretic medications, particularly thiazide diuretics
- Vomiting, diarrhea, or excessive sweating
- Heart failure, kidney disease, and liver disease
- A condition called SIADH (syndrome of inappropriate antidiuretic hormone), which can be caused by certain medications, lung disease, or other conditions
- Addison’s disease (adrenal insufficiency)
- Severe burns or other major fluid losses
Causes of high sodium (hypernatremia):
- Dehydration, the most common cause
- Excessive sweating, fever, or burns without enough fluid replacement
- Diabetes insipidus, a condition in which the kidneys cannot conserve water
- Kidney disease
- Eating very salty foods (rare as a sole cause)
Sodium abnormalities are often more about water balance than about salt itself — a low sodium level usually means too much water relative to sodium, not literally too little salt in the body.
Potassium (K)
Potassium is an electrolyte that is essential for the proper function of the heart, nerves, and muscles. Even small abnormalities in potassium can cause irregular heartbeats and muscle weakness, so potassium results are watched closely.
A typical reference range for adults is 3.5–5.0 millimoles per litre (mmol/L) or milliequivalents per litre (mEq/L).
Causes of low potassium (hypokalemia):
- Diuretic medications, particularly loop and thiazide diuretics
- Vomiting and diarrhea
- Inadequate dietary intake (rare in healthy people)
- Certain medications, including some asthma medications and corticosteroids
- Kidney disease in some forms
- Hyperaldosteronism (excess aldosterone hormone)
- Refeeding syndrome (when severely malnourished people resume eating)
Causes of high potassium (hyperkalemia):
- Kidney disease, particularly when significantly impaired
- Medications including ACE inhibitors, angiotensin receptor blockers, potassium-sparing diuretics, and some chemotherapy drugs
- Severe injury, burns, or muscle breakdown
- Addison’s disease
- A common laboratory artifact in which potassium leaks out of red blood cells during sample collection (called pseudohyperkalemia) — your doctor may want to repeat the test if a high potassium level is unexpected
High potassium can be a medical emergency because it can trigger life-threatening abnormal heart rhythms. Significantly elevated potassium results are usually flagged urgently by the laboratory.
Chloride (Cl)
Chloride is an electrolyte that, along with sodium, helps maintain fluid balance and acid-base balance in the body. It is one of the main negatively charged ions in the blood.
A typical reference range for adults is 96–106 mmol/L.
Chloride levels usually move in parallel with sodium, so abnormal chloride often reflects the same underlying cause as a sodium abnormality (dehydration, fluid overload, vomiting, or diarrhea). Chloride is sometimes most useful when interpreted together with bicarbonate to assess acid-base disorders.
Bicarbonate (CO2 or HCO3)
Bicarbonate is a chemical that the body uses to maintain acid-base balance — keeping the blood’s pH within a narrow normal range. The BMP measures total carbon dioxide content in the blood, which is mostly bicarbonate, and is reported as either CO2 or HCO3.
A typical reference range for adults is 22–29 mmol/L.
Causes of low bicarbonate (acidosis):
- Severe diarrhea
- Diabetic ketoacidosis
- Kidney disease
- Sepsis or other causes of poor tissue oxygen delivery
- Certain poisonings (including aspirin and methanol)
Causes of high bicarbonate (alkalosis):
- Persistent vomiting
- Diuretic medications
- Severe potassium deficiency
- Chronic lung disease such as COPD
Blood urea nitrogen (BUN)
Blood urea nitrogen is the amount of nitrogen in the blood that comes from urea, a waste product produced when the body breaks down protein. The kidneys filter urea out of the blood and excrete it in urine, so BUN provides information about kidney function. However, BUN is also affected by hydration status, dietary protein intake, and other factors.
A typical reference range for adults is 6–20 milligrams per decilitre (mg/dL).
Causes of high BUN:
- Kidney disease, the most common cause of a persistently elevated BUN
- Dehydration
- High dietary protein intake
- Gastrointestinal bleeding (the digested blood is a protein source)
- Heart failure or any condition reducing blood flow to the kidneys
- Certain medications, including corticosteroids
Causes of low BUN:
- Severe liver disease (the liver makes urea)
- Low dietary protein intake
- Pregnancy
- Overhydration
BUN is usually interpreted alongside creatinine. The BUN-to-creatinine ratio can help distinguish between different causes of kidney dysfunction.
Creatinine
Creatinine is a waste product produced by normal muscle activity. It is removed from the blood by the kidneys and excreted in urine. Because production is fairly steady from day to day, blood creatinine is one of the most reliable measures of kidney function — when the kidneys are not filtering normally, creatinine builds up in the blood.
A typical reference range for adults is 0.84–1.21 mg/dL, though the range varies somewhat based on age, sex, and body size. People with more muscle mass typically have higher baseline creatinine levels.
Most laboratories report creatinine alongside an estimated glomerular filtration rate (eGFR), which is a calculated estimate of how well the kidneys are filtering blood. A typical normal eGFR is 90 mL/min/1.73m² or higher. An eGFR below 60 sustained for at least three months is the standard definition of chronic kidney disease.
Causes of high creatinine (impaired kidney function):
- Acute kidney injury, which can be caused by dehydration, low blood pressure, certain medications, or obstruction of the urinary tract
- Chronic kidney disease, often caused by diabetes, high blood pressure, or other chronic conditions
- Heart failure
- Certain medications, including some antibiotics, NSAIDs, and contrast dyes used in imaging
- Severe muscle injury (rhabdomyolysis)
Causes of low creatinine:
- Reduced muscle mass, including in older adults
- Severe liver disease
- Pregnancy
For a more detailed explanation of kidney function tests, see our companion article Understanding your kidney function tests.
Glucose
Glucose is the main sugar in the blood and the body’s primary source of energy. The body controls blood glucose tightly through hormones, particularly insulin. Abnormal blood glucose is the defining feature of diabetes.
The reference range depends on whether the test was done fasting or not:
- Fasting glucose (after at least 8 hours without food): a typical reference range is 70–99 mg/dL. Values of 100–125 mg/dL are typically classified as prediabetes; 126 mg/dL or higher on more than one occasion meets the criteria for diabetes.
- Random (non-fasting) glucose: values up to about 140 mg/dL are typical. A random glucose of 200 mg/dL or higher in someone with symptoms of diabetes meets the criteria for diabetes.
Causes of high glucose (hyperglycemia):
- Diabetes (type 1, type 2, or gestational)
- Stress, including acute illness, infection, or recent surgery
- Corticosteroid medications such as prednisone
- Eating before a “fasting” test
- Pancreatic conditions that reduce insulin production
- Certain hormone disorders (Cushing’s syndrome, acromegaly, hyperthyroidism)
Causes of low glucose (hypoglycemia):
- Diabetes medications, particularly insulin and some oral diabetes drugs
- Prolonged fasting
- Excessive alcohol intake
- Severe liver or kidney disease
- Adrenal insufficiency
- Certain rare hormone-producing tumours
For a deeper discussion of diabetes testing, see our companion articles Understanding your hemoglobin A1c result and Understanding your fasting glucose and oral glucose tolerance test.
Calcium
Calcium is a mineral that is essential for strong bones and teeth, blood clotting, and the function of nerves, muscles, and the heart. Most of the body’s calcium is stored in bone, and only a small fraction circulates in the blood, but that fraction is tightly regulated.
A typical reference range for total calcium in adults is 8.5–10.2 mg/dL.
Causes of high calcium (hypercalcemia):
- Hyperparathyroidism, a condition in which the parathyroid glands produce too much parathyroid hormone (PTH), the most common cause
- Cancer, including some that produce a PTH-like substance (such as squamous cell lung cancer) and others that spread to bone (such as breast cancer and multiple myeloma)
- Vitamin D excess
- Certain medications, including thiazide diuretics and lithium
- Long periods of immobility
- Inflammatory conditions such as sarcoidosis
Causes of low calcium (hypocalcemia):
- Hypoparathyroidism (too little PTH), often after thyroid or parathyroid surgery
- Vitamin D deficiency
- Chronic kidney disease
- Severe magnesium deficiency
- Acute pancreatitis
- Certain medications
Calcium results are sometimes reported alongside ionized calcium, which measures only the biologically active form of calcium and is not affected by changes in protein levels. Ionized calcium is more accurate but is not part of the routine BMP.
What happens after a BMP?
If your BMP results are within reference ranges, no further investigation is usually needed. If a result is abnormal, the next steps depend on which measurement is abnormal, by how much, and what other findings are present. Some possibilities include:
- Repeat the test. Mildly abnormal results may resolve on their own or be due to laboratory variability. A repeat test can confirm whether the abnormality is real and persistent.
- Add additional blood tests. Specific patterns prompt targeted follow-up. For example, an elevated calcium often prompts PTH, vitamin D, and phosphorus testing. An elevated creatinine may prompt repeat testing alongside a urine albumin-to-creatinine ratio. An elevated glucose typically prompts hemoglobin A1c testing.
- Order imaging. Persistent kidney abnormalities may prompt an ultrasound of the kidneys.
- Adjust medications. Some abnormalities — particularly involving potassium, sodium, or kidney function — may prompt your doctor to change a dose or stop a medication.
- Review diet and fluid intake. Some abnormalities, particularly involving sodium, glucose, or BUN, can be improved by dietary changes.
- Refer to a specialist. Persistent or significant kidney function abnormalities may prompt referral to a nephrologist (kidney specialist). Calcium and parathyroid abnormalities may prompt referral to an endocrinologist.
An abnormal BMP result is not in itself a diagnosis. The BMP is a starting point, and your doctor will interpret the results in the context of your symptoms, medical history, medications, and any other test results.
Questions to ask your doctor
- Were any of my BMP results outside the reference range?
- If a result is abnormal, how significant is the abnormality?
- Could any of my medications be affecting my results?
- Should the test be repeated, and if so, when?
- Do I need any follow-up tests, such as a comprehensive metabolic panel, hemoglobin A1c, or imaging?
- What is my eGFR, and what does it mean for my kidney function?
- Are there changes I can make to my diet, fluid intake, or activity that would improve my results?
- Do I need to see a specialist?
Related articles on MyPathologyReport.com
- Understanding your comprehensive metabolic panel (CMP)
- Understanding your kidney function tests
- Understanding your liver panel
- Understanding your hemoglobin A1c result
- Understanding your fasting glucose and oral glucose tolerance test
- Understanding your parathyroid hormone (PTH) and calcium balance tests
- Multiple myeloma
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