In diagnostic circles, BUN is the acronym for Blood Urea Nitrogen – a test recommended by physicians to check the working of the kidneys. While Blood Urea Nitrogen or BUN can be a stand-alone, it is mostly part of a battery of tests required to ascertain kidney function.

Blood Urea Nitrogen

Urea is a waste product that is removed by the kidneys through urine. It reaches the kidneys from the liver. The liver breaks down protein from food, releasing nitrogen-containing ammonia into the bloodstream. Nitrogen combines with oxygen, hydrogen and carbon to form urea.

High BUN levels

Urea that reaches the kidneys is filtered out through urine, leaving a negligible amount in the bloodstream. When the kidneys are not able to perform this filter function efficiently, there is an increase in the level of urea in the blood, and this is detected during a Blood Urea Nitrogen or BUN test.

Besides the kidneys, there are other factors that increase BUN levels (viz) high-protein foods, first trimester of pregnancy, gastrointestinal bleeding, dehydration, stress levels, burns and aging.

Low BUN levels

Overhydration or drinking too much water can show up as low BUN levels. Eating a diet low in protein, malnourishment and liver disease also cause BUN levels to dip.

Conditions/Symptoms that lead to a BUN test

• Swollen arms, legs, feet, face and the area circling the eyes
• Increase in urinating frequency
• Frothy, bloody or discoloured urine
• Frequent muscle cramps
• Unexplainable tiredness
• Back pain
• Existing kidney disease or cardiovascular disease
• High blood pressure or diabetes

A Blood Urea Nitrogen Test is also taken as part of a routine health check.

Taking the test

It is taken through a blood sample from the inside of the arm or back of the hand. Since it is part of a panel, fasting for 8-12 hours before the test may be required. However, if BUN is taken alone, it can be taken as a random test.

Diagnosis and Result

The sample is sent to the lab for diagnosis and the result is received within a few days.

It is important to know that a Creatinine Test is recommended along with a Blood Urea Nitrogen or BUN test to ensure accuracy while checking for kidney health.