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Causes of high and low urea in the blood
Medical expert of the article
Last reviewed: 06.07.2025
A reduced concentration of urea in the blood does not have any particular diagnostic significance; it is possible after the administration of glucose, with reduced protein catabolism, increased diuresis, after hemodialysis (for example, in case of poisoning), during starvation, and in case of liver failure.
There are three groups of causes that lead to an increase in the concentration of urea in the blood: adrenal, renal and subrenal azotemia.
- Adrenal azotemia is also called production azotemia, as it is caused by increased formation of nitrogenous wastes in the body. This type of azotemia is observed when consuming very large amounts of protein food, various inflammatory processes with a pronounced increase in protein catabolism, dehydration as a result of vomiting, diarrhea, etc. In these conditions, excess urea is quickly removed from the body by the kidneys. A prolonged increase in the urea content in the blood serum above 8.3 mmol / l should be regarded as a manifestation of renal failure.
- Increased urea concentration in the blood most often occurs as a result of impaired renal excretory function. Renal (retention) azotemia can be caused by the following forms of pathology.
- Acute and chronic glomerulonephritis; in acute glomerulonephritis, an increase in urea concentration occurs rarely and, as a rule, it is short-term; in chronic glomerulonephritis, the urea content can fluctuate, increasing during an exacerbation of the process and decreasing when it subsides.
- Chronic pyelonephritis; the increase in urea concentration in these patients depends on the severity of nephrosclerosis and the inflammatory process in the kidneys.
- Nephrosclerosis caused by poisoning with mercury salts, glycols, dichloroethane, and other toxic substances.
- Crush syndrome; the concentration of urea in the blood can be very high, which is explained by a combination of delayed urea excretion and increased protein breakdown.
- Arterial hypertension with malignant course.
- Hydronephrosis, severe polycystic disease, tuberculosis of the kidney.
- Amyloid or amyloid-lipoid nephrosis; an increase in urea in the blood in such patients is observed only in the late stages of the disease.
- Acute renal failure (ARF); the blood urea concentration often reaches very high values - 133.2-149.8 mmol/l. The magnitude of the increase in the urea level in patients with ARF is of great importance. Thus, in uncomplicated cases, the concentration of urea in the blood increases by 5-10 mmol/l/day, and in the presence of infection or extensive trauma it increases by 25 mmol/l/day.
- Subrenal azotemia is a type of retention azotemia and occurs when urine excretion is delayed by some obstruction in the urinary tract (stone, tumor, in particular adenoma or prostate cancer).
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