Which of the following is the best time to collect a urine sample to evaluate the specific gravity of a canine patient?

• A. First morning
• B. Midday
• C. Late afternoon
• D. Last sample of the day

Answer: (A)

Specific gravity shows how concentrated the urine is, and that concentration is most pronounced when the animal has gone several hours without drinking. The first morning urine is typically the most concentrated because the dog hasn’t had recent water intake and has had time to reabsorb water overnight. This gives a higher, more consistent SG value that best reflects the kidneys’ concentrating ability. Samples collected later in the day tend to be more diluted due to ongoing fluid intake and normal diuresis, which can mask the true renal concentrating function. So, capturing the first morning urine provides the most reliable measurement for evaluating specific gravity.