Vitamin C (Ascorbic Acid) 24-Hour Urinary Rate

Why This Test Is Done

Your healthcare provider may order this test if you have symptoms of vitamin C deficiency (like fatigue, frequent infections, or slow wound healing) or if you’re taking high doses of vitamin C supplements. It can also be used to monitor kidney function or detect certain metabolic conditions.

What to Expect Before the Test

You’ll need to collect all your urine for a full 24-hour period, typically starting after midnight one day and ending the same time the next day. Drink plenty of fluids to help urine flow, but avoid excessive caffeine or alcohol. Follow your provider’s instructions carefully to ensure accurate results.

What Happens During the Test

No special preparation is needed beyond collecting urine samples. You’ll likely be given a clean container to store the urine in a fridge until you return it to the lab. The lab will analyze the sample to measure vitamin C levels.

What the Results Mean

Results are usually reported as the total amount of vitamin C excreted in the urine over 24 hours. While reference ranges vary by lab, lower than expected levels may suggest poor absorption or vitamin C deficiency, while very high levels could indicate over-supplementation or certain kidney conditions.