What is the reference range for Blood Urea Nitrogen?

The standard reference range for Blood Urea Nitrogen is Approximately 2.5–7.1 mmol/L (7–20 mg/dL), age- and laboratory-specific.. Reference ranges vary by laboratory and assay platform — interpret in context of the issuing laboratory's stated range.

Which tests measure Blood Urea Nitrogen?

Blood Urea Nitrogen is measured in 2 tests on BiomarkersLabs.com, including Basic Metabolic Panel without Calcium, Comprehensive Metabolic Panel with Adjusted Calcium, Plasma.

Biomarker Reference · BUN

What does the Blood Urea Nitrogen test measure?

Blood Urea Nitrogen (BUN) is a clinical biomarker used in metabolic-diabetes assessment. Urea is synthesised in the liver from ammonia generated during amino-acid catabolism and is excreted by the kidneys. It is measured in 2 laboratory tests on BiomarkersLabs.com.

Reference Range: Approximately 2.5–7.1 mmol/L (7–20 mg/dL), age- and laboratory-specific.
Units: mg/dL, mmol/L
Measured In: 2 tests
Category: Metabolic

Functional medicine optimal10–18 mg/dL (3.6–6.4 mmol/L) is considered physiologically typical in well-hydrated individuals with normal renal function and protein intake.

What is Blood Urea Nitrogen?

Urea is synthesised in the liver from ammonia generated during amino-acid catabolism and is excreted by the kidneys. Its plasma concentration reflects the balance between protein intake, hepatic urea synthesis, and renal clearance. Because urea is freely filtered and variably reabsorbed along the nephron—especially when urine flow is low—BUN is influenced by both GFR and volume status.

Why is Blood Urea Nitrogen measured?

Elevated BUN can signal reduced GFR (acute or chronic kidney disease), volume depletion (pre-renal azotaemia), high protein intake, gastrointestinal bleeding, or catabolic states. A disproportionately high BUN relative to creatinine (BUN:creatinine ratio above 20:1) suggests pre-renal azotaemia or gastrointestinal bleeding. Low BUN is less clinically significant but may accompany liver disease, overhydration, or very low protein intake.

Reference ranges

Standard reference: Approximately 2.5–7.1 mmol/L (7–20 mg/dL), age- and laboratory-specific.
Functional medicine optimal: 10–18 mg/dL (3.6–6.4 mmol/L) is considered physiologically typical in well-hydrated individuals with normal renal function and protein intake.
Units: mg/dL, mmol/L

Reference ranges vary by laboratory and assay platform. Interpret in context of the issuing laboratory's stated range.

Tests that measure Blood Urea Nitrogen

2 tests on BiomarkersLabs.com include this biomarker.

BML-MET-021Comprehensive

Basic Metabolic Panel without Calcium

Blood Urea Nitrogen reference range in this test: Approximately 7–20 mg/dL (2.5–7.1 mmol/L); assay-specific.

BML-MET-026Comprehensive

Comprehensive Metabolic Panel with Adjusted Calcium, Plasma

Blood Urea Nitrogen reference range in this test: Approximately 2.5–7.1 mmol/L (7–20 mg/dL), age- and laboratory-specific.

Related clinical conditions

Related Biomarkers

Frequently measured alongside

SodiumNa6 tests PotassiumK6 tests ChlorideCl6 tests Total Carbon Dioxide (Bicarbonate)CO₂1 test Serum CreatinineCr6 tests GlucoseGluc6 tests BUN:Creatinine RatioBUN:Cr3 tests Glucose, PlasmaGluc1 test

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