What is the Normal Range for Urea Levels?
Currently, the most commonly used methods for urea measurement in clinical laboratories include diacetyl monoxime method, enzyme-coupled ultraviolet spectrophotometry, and o-phthalaldehyde method. Generally, a urea level between 2.0 and 7.1 mmol/L is considered normal.
1. Elevated levels:
(1) Renal diseases such as acute renal failure, chronic nephritis, renal vascular sclerosis, chronic pyelonephritis, renal tuberculosis, and advanced renal tumors. When renal function is mildly impaired, BUN may remain unchanged. However, when 60% to 70% of effective nephron units are damaged, BUN levels increase.
(2) Pre-renal or post-renal factors that significantly reduce urine output or cause anuria, such as dehydration from severe vomiting or diarrhea, edema, ascites, circulatory failure, as well as urinary obstruction caused by urinary stones, prostatic hypertrophy, or tumors.
(3) Excessive breakdown of proteins in the body, such as extensive burns, post-major surgery, upper gastrointestinal bleeding, hyperthyroidism, and acute infectious diseases. In these cases, BUN levels may increase while other renal function test results remain largely normal.
2. Decreased levels: Less commonly observed. This is mainly due to liver parenchymal damage, resulting in reduced production. Conditions such as acute yellow atrophy of the liver, liver cirrhosis, toxic hepatitis, and severe anemia can lead to decreased urea levels.
Populations that need to be tested include individuals with severe vomiting, diarrhea, extensive burns, and abnormal renal function.
Before the test: Avoid strenuous exercise and maintain a good diet and sleep schedule. Plasma (or serum) urea content is closely related to the protein intake in the diet. High-protein diets can significantly increase urea levels in the plasma (or serum), while low-protein diets can significantly reduce them.
During the test: Discard a portion of the initial urine to flush out bacteria that may be present in the urethra and anterior urethra. Then, collect the midstream urine sample for testing.
