The Chem 6 panel — also called a Basic Metabolic Panel (BMP) or SMAC-6 — is one of the most frequently ordered blood tests in medicine. It gives your doctor a rapid snapshot of kidney function, fluid and electrolyte balance, and blood glucose in six measurements from a single tube of blood.
The Six Tests in a Chem 6 Panel
1. Blood Urea Nitrogen (BUN)
What it measures: BUN reflects urea nitrogen — a waste product from protein metabolism filtered by the kidneys. It is one of the primary markers of kidney function.
Normal range: 7–25 mg/dL
High BUN causes: kidney disease or failure, severe dehydration (concentrated blood), high-protein diet, GI bleeding (blood digested as protein), or heart failure (reduced kidney perfusion).
Low BUN causes: liver disease (liver cannot synthesize urea), malnutrition, or overhydration.
2. Creatinine
What it measures: Creatinine is a waste product from muscle metabolism excreted exclusively by the kidneys. It is the most reliable single marker of kidney function in the Chem 6.
Normal range: 0.6–1.2 mg/dL (men); 0.5–1.1 mg/dL (women)
High creatinine causes: acute or chronic kidney disease, dehydration, high muscle mass, or medications (NSAIDs, some antibiotics, ACE inhibitors at high doses).
BUN-to-creatinine ratio: (normal: 10–20:1) helps differentiate pre-renal azotemia (dehydration) from intrinsic kidney disease.
3. Glucose
What it measures: blood sugar level at the time of draw. Fasting and non-fasting reference ranges differ.
Normal fasting range: 70–99 mg/dL; Prediabetes: 100–125 mg/dL; Diabetes: ≥126 mg/dL on two separate occasions; Hypoglycemia: below 70 mg/dL.
A single high glucose on a non-fasting draw is not diagnostic of diabetes — confirmation with a fasting value or HbA1c is required.
4. Sodium (Na+)
What it measures: the primary extracellular electrolyte regulating fluid balance, nerve conduction, and blood pressure.
Normal range: 136–145 mEq/L
Low sodium (hyponatremia, <136): heart failure, liver cirrhosis, kidney disease, SIADH, hypothyroidism, excessive water intake, diuretics or antidepressants.
High sodium (hypernatremia, >145): dehydration, diabetes insipidus, insufficient fluid intake.
5. Potassium (K+)
What it measures: the primary intracellular electrolyte critical for cardiac rhythm and muscle function. Potassium has the narrowest safe range on the Chem 6.
Normal range: 3.5–5.0 mEq/L
Low potassium (hypokalemia, <3.5): diarrhea, vomiting, diuretics, poor dietary intake, or metabolic alkalosis. Risk: cardiac arrhythmias and muscle weakness.
High potassium (hyperkalemia, >5.0): kidney failure, ACE inhibitors, potassium-sparing diuretics, or hemolyzed sample (falsely elevated). Severe hyperkalemia (>6.5 mEq/L) is a medical emergency.
6. Carbon Dioxide (CO2) / Bicarbonate
What it measures: bicarbonate (HCO3-), the main buffer in your blood's acid-base system — reflecting whether your blood pH is balanced, acidic, or alkaline.
Normal range: 22–29 mEq/L
Low CO2 (metabolic acidosis): diabetic ketoacidosis (DKA), kidney disease, diarrhea, lactic acidosis, or aspirin toxicity.
High CO2 (metabolic alkalosis): vomiting, diuretic use, or primary hyperaldosteronism.
Chem 6 vs. Chem 7, Chem 8, and CMP
- Chem 6 / BMP: BUN, creatinine, glucose, sodium, potassium, bicarbonate
- Chem 7 / BMP + Chloride: adds chloride (Cl-) for a more complete electrolyte picture
- Chem 8: typically adds calcium to the above seven values
- CMP (Comprehensive Metabolic Panel): the BMP plus liver function tests (AST, ALT, alkaline phosphatase, bilirubin) and albumin — 14 values total
When Is a Chem 6 Ordered?
Annual wellness screening (baseline kidney function and glucose), diabetes monitoring (glucose and kidney function affect medication choice for patients on metformin), hypertension management (potassium and sodium monitoring on diuretics or ACE inhibitors), pre-operative assessment, and hospital/emergency monitoring of acutely ill patients.
What if One Value Is Slightly Off?
A single value mildly outside the reference range in an otherwise healthy person often requires context rather than alarm. Your doctor will look at trends, related values, and your symptoms. Never interpret a single value without clinical context.
Get Your Chem Panel Done at Home
A Chem 6 or BMP requires just one tube of blood and typically produces results within 24 hours. Speedy Sticks handles all standard panel types at home and routes samples to your chosen reference lab. Book a visit today.
This content is for informational purposes only and is not a substitute for professional medical advice. Consult your physician about your specific lab results.
How to interpret your Chem 6 results in combination
Individual out-of-range values are informative, but the real diagnostic value of the Chem 6 comes from reading the markers together. Several combinations point clearly to specific conditions:
- High BUN + high creatinine: The foundational pattern for kidney impairment. The BUN-to-creatinine ratio refines the picture: a ratio above 20:1 suggests pre-renal azotemia (dehydration, poor kidney perfusion from heart failure) rather than intrinsic kidney disease, where the ratio is typically 10–15:1.
- High creatinine + normal BUN: Can indicate rhabdomyolysis (muscle breakdown flooding the blood with creatinine), trimethoprim use (blocks tubular creatinine secretion — a measurement artifact, not true kidney damage), or high muscle mass in athletes.
- Low sodium + low glucose: Seen in adrenal insufficiency (Addison's disease), where cortisol and aldosterone deficiency affect both markers simultaneously.
- High potassium + high creatinine + high BUN: Hyperkalemia in the context of kidney failure. Potassium above 6.0 mEq/L with kidney impairment is a potential cardiac emergency — the kidneys are failing to excrete potassium normally.
- Low potassium + low chloride + high CO₂: The classic metabolic alkalosis pattern from prolonged vomiting or aggressive diuretic use. Loop diuretics dump potassium and chloride into the urine while the kidneys retain bicarbonate (CO₂) to compensate.
- High glucose + high sodium + elevated BUN/creatinine: Suggests hyperglycemic hyperosmolar state (HHS) — severe dehydration and blood concentration from very high blood sugar. A medical emergency in uncontrolled Type 2 diabetes.
eGFR: the calculated kidney function score
When a Chem 6 is ordered, most labs automatically calculate and report the eGFR (estimated glomerular filtration rate) from the creatinine result alongside the patient's age and sex. eGFR is the primary metric used to stage chronic kidney disease:
- eGFR ≥90 — normal kidney function (in the absence of other kidney damage markers)
- eGFR 60–89 — mildly decreased; usually monitored without intervention
- eGFR 45–59 — CKD Stage 3a; nephrology evaluation often recommended
- eGFR 30–44 — CKD Stage 3b; medication dose adjustments, close monitoring
- eGFR 15–29 — CKD Stage 4; preparation for kidney replacement therapy
- eGFR below 15 — CKD Stage 5 (kidney failure); dialysis or transplant
A single low eGFR is less meaningful than a trend. An eGFR that has declined from 75 to 52 over two years represents active disease progression even if 52 is not critically low in isolation.
How often is a Chem 6 ordered?
Frequency depends on why it is being monitored:
- Healthy adults, no chronic conditions — typically included in annual wellness bloodwork or ordered when symptoms warrant evaluation.
- Hypertension on ACE inhibitors or ARBs — 1–2 weeks after starting or adjusting dose (potassium and creatinine), then at least annually once stable.
- Diuretic therapy — 2–4 weeks after initiation or dose change (potassium, sodium), then every 3–6 months.
- Chronic kidney disease — every 3–6 months for Stage 3; monthly for Stage 4–5.
- Diabetes management — at least annually; more frequently if kidney function is declining or medications are being adjusted.
- Hospital inpatients — daily or every 2–3 days in the ICU; on admission for all acute presentations.
Sources and further reading
Chem 6 Panel Drawn at Home
Sodium, potassium, creatinine, BUN, glucose, CO2 — your Chem 6 can be collected at home. A certified phlebotomist comes to you with your provider's order.
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