Blood Urea Nitrogen (BUN) Test

The Blood Urea Nitrogen (BUN) test measures nitrogen waste from protein metabolism in the blood. It is used to assess kidney function (kidneys excrete BUN — impaired kidneys cause it to accumulate), detect dehydration (raises BUN disproportionately relative to creatinine), identify upper GI bleeding (digested blood raises BUN dramatically), and monitor CKD progression. It is a standard component of the Kidney Function Test (KFT) / Renal Function Test (RFT) panel.

No fasting is required. However, avoid an unusually high-protein meal the night before, as a very large protein load can transiently raise BUN. Normal dietary habits are fine. Inform your Medall team of any medications, as some (corticosteroids, tetracyclines) can raise BUN.

When blood enters the gastrointestinal tract — from a bleeding peptic ulcer, oesophageal varices, or other upper GI source — it is digested and absorbed as protein. The liver converts this additional protein into urea, dramatically raising BUN. This is called a 'protein load' effect. A BUN:Creatinine ratio above 20:1 in the setting of suspected GI bleeding is a useful clinical clue pointing to an upper GI source, as lower GI bleeding does not cause the same protein load.

Azotaemia means elevated nitrogen-containing compounds (primarily urea and creatinine) in the blood — it is the laboratory finding of kidney failure or impaired kidney clearance. Pre-renal azotaemia occurs when kidneys are functional but not receiving enough blood flow (dehydration, heart failure). Renal azotaemia occurs from intrinsic kidney damage. Post-renal azotaemia occurs from urinary tract obstruction blocking urine output. Identifying which type guides treatment.

Both BUN and creatinine rise when kidney function declines, but they are affected differently by non-kidney factors. BUN is influenced by protein intake, hydration, and GI bleeding — it can be elevated even with normal kidneys. Creatinine is more specific to kidney filtration and muscle mass, less affected by diet. Together — especially as the BUN:Creatinine ratio — they provide more accurate clinical information than either alone.

Report delivery is typically within 6 hours of sample collection and sent directly to your email and WhatsApp.

Book online at medall.in, through the Medall app, by calling +91 7550 177 777, or via WhatsApp. Home sample collection is available — our certified phlebotomist comes to you at your chosen time.

They measure the same waste product from the same metabolic pathway. BUN reports only the nitrogen fraction (in mg/dL of nitrogen). Serum Urea reports the entire urea molecule (in mg/dL of urea). Serum Urea is approximately 2.14 times the BUN value. Both are clinically equivalent markers of kidney function — the choice of which is reported depends on laboratory and physician convention. S5 — MOST BOOKED TESTS AT MEDALL Most Booked Tests at Medall Trusted by millions of patients across South India — these are the tests our doctors recommend most. Test Price Description Complete Blood Count (CBC) ₹X/* Screens for anaemia, infections, and immune health Thyroid Profile (T3, T4, TSH) ₹X/* Detects hypothyroidism, hyperthyroidism, and thyroid disorders HbA1c — Diabetes Monitoring ₹X/* 3-month average blood sugar — essential for diabetes management Liver Function Test (LFT) ₹X/* Complete liver health panel including ALT, AST, Albumin, Bilirubin & more [View All Popular Tests →]