Understanding Your Basic Metabolic Panel (BMP)

Section Editor: Christopher McCudden Ph.D., DABCC, FADLM, FCACB
June 23, 2026

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 (or unexpectedly normal) 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, and one of the most useful routine measures 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. Doctors often include part or all of a BMP during routine health check-ups, especially for people with risk factors or chronic conditions.

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 in the laboratory. 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, which requires 8 to 12 hours without food beforehand, or as a non-fasting test. Your doctor will tell you which to do. The other seven components are only minimally affected by eating, so fasting is not needed for them.

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 is essential for nerve signaling and muscle contraction.

A typical reference range for adults is 135–145 milliequivalents per liter (mEq/L) or millimoles per liter (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 syndrome of inappropriate antidiuretic hormone (SIADH), 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 levels can cause irregular heartbeats and muscle weakness, so potassium results are closely monitored.

A typical reference range for adults is 3.5–5.0 millimoles per liter (mmol/L) or milliequivalents per liter (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
Potassium can sometimes look falsely high (a lab finding called pseudohyperkalemia), often when blood cells are damaged during the blood draw or while the sample is being handled (a process called hemolysis). This can happen with a difficult blood draw, a tourniquet left on too long, clenching the fist during the draw, a delay in processing the sample, or a very high white blood cell count. If the result is unexpectedly high, your doctor may repeat the test.

High potassium can be a medical emergency because it can trigger life-threatening abnormal heart rhythms. Significantly elevated potassium levels are usually flagged by the laboratory for urgent attention.

Chloride (Cl)

Chloride is an electrolyte that, along with sodium, helps maintain fluid balance and acid-base balance in the body. It is the main negatively charged electrolyte (called an anion) 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 the total carbon dioxide (CO2) content in the blood, which is mostly bicarbonate, and on your report it may be labeled CO2, total 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 chronic obstructive pulmonary disease (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 deciliter (mg/dL), or 2.1–7.1 mmol/L.

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.

Typical reference ranges differ for men and women: about 74–110 µmol/L (0.84–1.24 mg/dL) for men and 45–90 µmol/L (0.51–1.02 mg/dL) for women. The range also varies somewhat based on age, diet, 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), a calculated estimate of how well the kidneys filter blood. An eGFR of 90 mL/min/1.73m² or higher is generally considered normal in younger adults with healthy kidneys. eGFR naturally declines somewhat with age, and kidney disease is usually diagnosed using eGFR along with urine findings and evidence of sustained change over time. For example, an eGFR below 60 for at least 3 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 tightly regulates blood glucose through hormones, particularly insulin. Abnormally high or low 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 (3.9–5.5 mmol/L). Values of 100–125 mg/dL (5.6–6.9 mmol/L) are typically classified as prediabetes; values of 126 mg/dL (7.0 mmol/L) or higher on more than one occasion meet the criteria for diabetes.
Random (non-fasting) glucose: values up to about 140 mg/dL (7.7 mmol/L) are typical. A random glucose of 200 mg/dL (11.1 mmol/L) 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 tumors

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. Because nearly half of the calcium in the blood is bound to proteins (especially albumin), an abnormal protein level can make the total calcium appear abnormal even when the active form (ionized calcium) is normal.

A typical reference range for total calcium in adults is 8.5–10.2 mg/dL (2.12–2.55 mmol/L).

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 reflect 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, elevated calcium often prompts testing of PTH, vitamin D, and phosphorus. An elevated creatinine level may prompt repeat testing, including 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?