What Could Be the Reason for High Creatinine and Low BUN?

High creatinine and low blood urea nitrogen may indicate several health scenarios, such as a high percentage of muscle mass, inadequate intake of protein, excessive intake of protein, dehydration and impaired kidney function, according to DaVita Kidney Care. Men tend to have higher BUN to creatinine ratios than women.

Creatinine is a waste product resulting primarily from the breakdown of ingested protein, from muscle metabolism and from muscle contractions, explains MedicineNet.com. The kidneys filter creatinine from the blood and excrete it as urine. Proper hydration and optimal health are essential for the kidneys to properly perform this function. Consequently, consuming excessive amounts of protein and not enough water can elevate creatinine levels in the blood.

BUN is a measure of the waste product of muscle breakdown. BUN tends to increase with dehydration, states Life Options. Contrarily, low BUN may mean that an individual is not consuming the minimum amount of protein his body requires, which forces the body to utilize existing protein, or muscle. Ideally, BUN should be higher than creatinine, and adult males should have an average BUN to creatinine ratio between 10:1 and 20:1, explains Lab Tests Online.

BUN to creatinine ratios that are too high or too low may also point to damaged kidneys or compromised kidney function. Damaged kidneys are a symptom of other underlying health conditions, according to DaVita Kidney Care.