What is urea? Urea is an organic compound found in urine and to a lesser extent in sweat. How it ends up in your urine is the kidneys extract it from your blood, under the control of antidiuretic hormone. Why urea is present in the blood is because your liver put it there.
Your liver is the organ where the urea is formed. It’s formation occurs when amino acids are broken down for energy and the ammonia by product is then converted to urea for excretion.
Essentially, urea is the mechanism for expelling potentially toxic nitrogen that’s produced when amino acids are catabolized. Because amino acids cannot be stored, they are in a constant state of being built or degraded in order to maintain health. As such, urea production and excretion is an ongoing process. By way of urine or sweat, you’ll excrete about 30 grams of it a day.
Measuring your urea levels in the blood is a way to evaluate your kidneys, what’s referred to as the BUN test. This test is often run as part of a complete blood work to confirm your kidneys are functioning normally. However, just a BUN test may be ordered to assess progression of kidney disease, damage (diabetes, hypertension) or failure and how well your kidney treatment, e.g. dialysis, is working.
Generally, an increase in blood levels of urea (known as uremia) indicates reduced kidney function. Yet, there are other causes for your test to show a BUN level rise, for instance:
- heart failure
- certain drugs
- intestinal bleeding
- Addison’s disease
- diet high in protein
- blockage ~ kidney stone, tumor
Liver disease (cirrhosis) or damage can produce lower than normal BUN test as well. Other possible causes for lower than normal urea levels in your blood are pregnancy, very low protein diet, malnutrition, over hydration and excessive release of antidiuretic hormone.
As you can see, an increase or decrease of urea levels does not automatically indicate kidney problems, but instead may be simply a matter of hydration or protein intake.
Also, urea is artificially made and used in fertilizers and medicine.