Basic Metabolic Panel
Overview
The basic metabolic panel (BMP), also called a Chem-7, is a frequently ordered blood test that provides a snapshot of key metabolic functions: electrolyte balance, kidney function, and blood glucose. The comprehensive metabolic panel (CMP) adds hepatic function tests (LFTs, albumin, bilirubin).
Reference intervals can vary slightly by institution and laboratory method, so values should always be interpreted against the reporting lab’s range.
Normal Values
| Component | Normal Range | Clinical Significance |
|---|---|---|
| Sodium (Na⁺) | 136–145 mEq/L | Volume and osmolality regulation |
| Potassium (K⁺) | 3.5–5.1 mEq/L | Cardiac and neuromuscular function |
| Chloride (Cl⁻) | 97–107 mEq/L | Acid-base balance; inversely related to HCO₃⁻ |
| CO₂ / Bicarbonate (HCO₃⁻) | 22–29 mEq/L | Acid-base buffer; kidney regulation |
| BUN (Blood Urea Nitrogen) | 7–20 mg/dL | Protein metabolism; renal clearance |
| Creatinine | 0.6–1.2 mg/dL | Muscle metabolism; glomerular filtration marker |
| Glucose (fasting) | 70–100 mg/dL | Carbohydrate metabolism; insulin function |
| Calcium (CMP only) | 8.6–10.2 mg/dL | Bone/muscle/nerve function; PTH regulated |
Common CMP Add-On Values
| Component | Typical Adult Range | Clinical Significance |
|---|---|---|
| Phosphorus | 3.0–4.5 mg/dL | Bone/mineral metabolism; ATP-related cellular function |
| Magnesium | 1.3–2.1 mEq/L | Neuromuscular stability and dysrhythmia risk modulation |
| Serum osmolality | 285–295 mOsm/kg H2O | Tonicity and free-water balance interpretation |
| Albumin | 3.5–5.5 g/dL | Oncotic pressure and protein status marker |
| Total protein | 5.5–8.3 g/dL | Combined albumin/globulin trend context |
| Total bilirubin | 0.1–1.2 mg/dL | Hepatic processing and hemolysis-related cue |
| AST | 9–25 U/L (female), 10–40 U/L (male) | Hepatocellular injury signal with ALT trend interpretation |
| ALT | 7–20 U/L (female), 10–55 U/L (male) | Hepatocellular injury signal with AST trend interpretation |
Component Interpretation
Sodium (Na⁺) 136–145 mEq/L
- Hyponatremia (<136): Confusion, lethargy, seizures (severe) — causes: SIADH, overhydration, heart failure
- Hypernatremia (>145): Thirst, agitation, seizures — causes: dehydration, diabetes insipidus, excessive sodium intake
- Sodium reflects fluid status — hyponatremia often means too much water relative to sodium, not always low total sodium
Potassium (K⁺) 3.5–5.1 mEq/L
- Hypokalemia (<3.5): Muscle weakness, cramps, constipation, U-waves on ECG, dangerous dysrhythmias
- Hyperkalemia (>5.1): Peaked T-waves on ECG, bradycardia, cardiac arrest — critical emergency at K⁺ >6.5 mEq/L
- Potassium levels change with pH: acidosis → hyperkalemia (K⁺ shifts out of cells); alkalosis → hypokalemia
Chloride (Cl⁻) 97–107 mEq/L
- Hypochloremia (<97): Often accompanies hyponatremia or metabolic alkalosis (vomiting)
- Hyperchloremia (>107): Often accompanies hypernatremia or metabolic acidosis (normal anion gap)
- Chloride and sodium trend in the same direction
CO₂ / Bicarbonate (HCO₃⁻) 22–29 mEq/L
- This is the total CO₂ or bicarbonate on a BMP — not the same as the PaCO₂ on an ABG
- Low HCO₃⁻ (<22): Metabolic acidosis — causes: DKA, lactic acidosis, renal failure, diarrhea
- High HCO₃⁻ (>29): Metabolic alkalosis — causes: vomiting, diuretic use, corticosteroids
BUN 7–20 mg/dL
- BUN reflects protein metabolism and renal clearance
- Elevated BUN: Dehydration (prerenal), renal failure, high protein diet, GI bleed (blood protein digested), muscle breakdown
- BUN:creatinine ratio >20:1 = prerenal cause (dehydration); 10–20:1 = intrinsic renal disease
Creatinine 0.6–1.2 mg/dL
- Creatinine is released from muscle metabolism at a constant rate and cleared by glomerular filtration — it’s the best routine marker of GFR (kidney function)
- Elevated creatinine: Renal insufficiency, rhabdomyolysis (muscle breakdown)
- eGFR (estimated glomerular filtration rate) is calculated from creatinine, age, sex, race — normal >60 mL/min/1.73m²
- Creatinine rises late — kidneys can compensate until ~50% nephron loss
Glucose 70–100 mg/dL (fasting)
- Hypoglycemia (<70): Diaphoresis, tremors, confusion, loss of consciousness — treat immediately with oral glucose or IV dextrose
- Hyperglycemia (>100): DM, stress hyperglycemia, corticosteroid use, TPN
- Diabetes criteria: Fasting glucose ≥126 mg/dL (on 2 occasions); random glucose ≥200 with symptoms
Common Clinical Patterns
| Pattern | Likely Cause |
|---|---|
| ↑BUN + ↑Creatinine (both) | Renal failure (acute or chronic) |
| ↑BUN alone, normal creatinine | Dehydration, GI bleed, high protein diet |
| ↓Na⁺ + ↓HCO₃⁻ | Vomiting with dehydration |
| ↓HCO₃⁻ + ↓K⁺ + ↑Glucose | Diabetic ketoacidosis (DKA) |
| ↑K⁺ + ↑Creatinine + ↓HCO₃⁻ | Renal failure |
Related Concepts
- anion-gap — Calculated from BMP components (Na⁺, Cl⁻, HCO₃⁻); helps classify metabolic acidosis.
- serum-calcium — Included in the comprehensive metabolic panel (CMP).
- sodium-balance-disorders — Full assessment and management of hyponatremia and hypernatremia.
- potassium-balance-disorders — Full assessment and management of hypokalemia and hyperkalemia.
- kidney-disease — BUN and creatinine as markers of CKD progression.
- diabetes-mellitus — BMP glucose and HCO₃⁻ interpretation in DKA.
Self-Check
- A patient’s BMP shows BUN 48 mg/dL and creatinine 0.9 mg/dL. What is the likely cause, and what does this ratio indicate?
- What ECG changes are associated with hyperkalemia, and why is this considered a life-threatening emergency?
- In a patient with DKA, which BMP values would you expect to be abnormal and in which direction?