A diluted urine sample contains more water than a typical specimen, leading to a lower concentration of dissolved substances. This makes accurate laboratory analysis challenging. Preventing dilution is important for valid diagnostic tests and screenings, ensuring the sample accurately reflects the body’s internal state.
Understanding Diluted Samples
Laboratories rely on specific markers to determine if a urine sample is diluted. Two primary indicators are specific gravity and creatinine levels. Specific gravity measures the concentration of all dissolved particles in urine compared to the density of water. A lower specific gravity indicates a higher water content relative to dissolved solids. Normal specific gravity typically ranges from 1.005 to 1.030, with values below this range often signaling dilution.
Creatinine is a waste product from muscle metabolism, filtered by the kidneys into urine. Its amount serves as another measure of urine concentration. Low creatinine levels in a urine sample suggest the specimen is less concentrated than expected, often due to excess water. Diluted urine samples commonly show creatinine levels below 20 mg/dL.
Factors Contributing to Dilution
The most common reason for a urine sample appearing diluted is overhydration. Consuming excessive fluids, especially water, shortly before providing a sample, significantly increases urine volume and reduces concentration. This occurs because the kidneys process excess fluid, leading to the excretion of more dilute urine.
Diuretics also contribute to diluted urine by increasing urine production. These include prescribed medications that promote fluid excretion or natural substances like coffee and some herbal teas. Additionally, some medical conditions can affect kidney function, impairing their ability to concentrate urine effectively. Conditions like diabetes insipidus cause the kidneys to pass too much fluid, resulting in large quantities of very dilute urine.
Strategies to Ensure Sample Integrity
Maintaining normal hydration is a primary strategy for ensuring a valid urine sample. Continue usual fluid intake and avoid consuming large amounts of water or other liquids immediately beforehand. An extra glass of water is generally sufficient; over-consuming fluids can lead to a diluted specimen.
Avoiding diuretic substances is also important before providing a urine sample. Limit intake of caffeinated beverages, certain teas, and any medications with diuretic effects, unless medically necessary.
Collecting the first urine of the morning is advisable. This “first morning void” is more concentrated due to reduced fluid intake overnight, offering a better reflection of the body’s baseline state.
Proper collection technique further contributes to sample integrity. A midstream clean-catch method is recommended, where the initial flow of urine is discarded before collecting the sample. This prevents contamination from bacteria or other substances, ensuring the collected sample accurately represents the urine from within the bladder.