What are kidney function tests?

Blood Tests

Serum Creatinine: A serum creatinine test measures the amount of creatinine, a waste product produced by muscle tissue breakdown, in your blood. This test helps determine how effectively kidneys remove creatinine from the bloodstream. A creatinine level higher than 1.2 mg/dL for women and 1.4 mg/dL for men indicates a kidney problem. For this test, a lower number is better. High creatinine levels can be a sign of acute kidney injury and chronic kidney disease.

Blood Urea Nitrogen (BUN) Test:  Urea nitrogen is a waste product found in the bloodstream, resulting from the breakdown of dietary protein. As you consume protein-rich foods, the body metabolizes them and produces urea nitrogen as a byproduct. The kidneys play a crucial role in filtering and removing urea nitrogen from the body as part of the waste elimination process. BUN (Blood Urea Nitrogen) levels can vary; typically, they tend to increase with age. The reference range for urea nitrogen typically falls between 7 and 20 mg/dL. Elevated BUN levels may indicate impaired kidney function; as kidney disease progresses, BUN levels tend to rise.

Estimated Glomerular Filtration Rate (eGFR) Calculation/Estimation:  It estimates how well kidneys are filtering waste products. GFR is calculated using equations considering factors such as creatinine levels, age, gender, and race.   A normal eGFR varies according to age and tends to decrease with age. In this test, a higher number is better. Typically, if your eGFR is lower than 60, it may indicate that the kidneys are not functioning properly. An eGFR lower than 15 is recognized as an indication of kidney failure.

Electrolyte Testing:  Assesses the levels of electrolytes (e.g., sodium, potassium, bicarbonate) in the blood. It helps evaluate the kidneys’ ability to maintain the appropriate balance of these substances.

Urine Test

Urinalysis: A urinalysis, or urine test, is a diagnostic procedure that involves analyzing various components of urine, including its physical properties, chemical composition, and microscopic elements. Urinalysis examines factors like urine colour, clarity, pH level, presence of proteins, glucose, ketones, blood, bilirubin, urobilinogen, nitrite, red and white blood cells, casts, and crystals.

A urinalysis is a valuable tool in diagnosing various conditions, such as urinary tract infections, kidney disease, and diabetes. It is often performed as part of routine check-ups when symptoms suggest urinary issues or as a follow-up to other medical investigations.

The urine albumin-creatinine ratio (uACR) test measures the levels of two substances in the urine: albumin (a protein) and creatinine. In a healthy kidney, albumin is retained in the blood while creatinine is filtered into the urine. Consequently, there should be minimal or no albumin present in the urine. The uACR is calculated by dividing the amount of urine albumin by the amount of urine creatinine, resulting in a ratio. A “normal” uACR level is typically below 30 mg/g. In this test, a lower uACR number is considered better. If the uACR level is 30 mg/g or higher, it may indicate albuminuria, which is the presence of elevated levels of albumin in the urine.

A 24-hour urine collection test is ordered to assess kidney stones, glomerular disease, or kidney function. It involves collecting all urine produced over a 24-hour period in a specialized container. This test is less common than others and is used when abnormal results are found in other tests or specific clinical situations.