If the glomerular filtration rate is 125 mL/min, approximately how many liters of filtrate are produced per day?

If the glomerular filtration rate is 125 mL/min, approximately how many liters of filtrate are produced per day?

• A. 120 L/day
• B. 180 L/day
• C. 240 L/day
• D. 60 L/day

Answer: (B)

Glomerular filtration rate tells us how much filtrate the kidneys produce each minute. To estimate daily filtrate, multiply by the minutes in an hour and by the hours in a day. 125 mL/min × 60 min = 7,500 mL/hour (7.5 L/hour). 7.5 L/hour × 24 hours = 180 L/day. So about 180 liters of filtrate are produced daily. The other numbers don’t fit because they would require a different per-minute rate to reach that daily total. Remember, most filtrate is reabsorbed, with only about 1–2 L becoming urine.

Glomerular filtration rate tells us how much filtrate the kidneys produce each minute. To estimate daily filtrate, multiply by the minutes in an hour and by the hours in a day.

125 mL/min × 60 min = 7,500 mL/hour (7.5 L/hour).

7.5 L/hour × 24 hours = 180 L/day.

So about 180 liters of filtrate are produced daily. The other numbers don’t fit because they would require a different per-minute rate to reach that daily total. Remember, most filtrate is reabsorbed, with only about 1–2 L becoming urine.