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24-Hour Urinary Nicotinamide (Vitamin B3) Excretion Rate

Published: August 9, 2026Updated: August 16, 2026

This test measures how much of the B vitamin niacin (vitamin B3) your body excretes in urine over 24 hours.

Quick summary

["Assessing niacin excretion helps evaluate how well your kidneys filter and process this essential vitamin."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
2656-7
Short code
Niacin 24h Ur-mRate
Synonyms
Niacin 24h Ur-mRate
Category
chemistry
Sample
urine
Container
Sterile urine container
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Specimen volume
10 mL
Stability
Room temperature: 2h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
4–24 hours
Order
routine

Why This Test Might Be Ordered

Your doctor may recommend this test if they suspect you have a condition affecting niacin metabolism, such as niacin deficiency, certain genetic disorders, or kidney function. It can also help monitor long-term vitamin intake or diagnose metabolic issues linked to niacin.

What to Expect Before the Test

No special preparation is needed, but you’ll provide a 24-hour urine collection starting from one point in time (often midnight) until the same time the next day. Drink plenty of water to help urine flow, but avoid certain medications or supplements that might interfere with results.

How the Test Works

Your urine sample is analyzed to measure the amount of niacin excreted. The test quantifies how much of this vitamin your body is processing and eliminating, which can reflect overall niacin status and kidney function.

What the Results Mean

Results help determine if niacin levels are appropriately processed and excreted. Abnormal results may indicate issues with niacin absorption, kidney disease, or metabolic disorders requiring further medical evaluation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Frequently asked questions

What does a low or high niacin excretion rate indicate?
Low excretion may suggest niacin deficiency, impaired kidney function, or certain metabolic disorders. High excretion could indicate overconsumption of niacin or conditions affecting its metabolism, such as genetic disorders.
How does this test differ from a niacin blood test?
This test measures niacin in urine over 24 hours, reflecting how much your body filters and excretes it. A blood test would measure niacin levels in your bloodstream at a single point in time, offering a different perspective on niacin status.
Can diet affect this test result?
Yes, dietary intake of niacin (found in foods like meat, poultry, fish, and fortified cereals) can influence results. Avoiding niacin-rich foods for a few days before testing may help standardize results, but always follow your healthcare provider’s instructions.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy