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24-Hour Vitamin B3 (Niacin) Intake Assessment

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

This test measures the amount of Vitamin B3 (niacin), a B-complex vitamin, consumed over a 24-hour period to help assess dietary intake and potential deficiencies.

Quick summary

["This test helps evaluate how much niacin you’re getting from your diet in a day."]

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

Key facts at a glance

LOINC
81135-6
Short code
Vit B3 intake 24h Est
Synonyms
Vit B3 intake 24h Est
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
20
Ref high
400
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
estimated
CPT
82670
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why This Test Is Done

Your healthcare provider may order this test if you have symptoms of niacin deficiency (such as fatigue, skin changes, or digestive issues) or if you’re following a special diet that affects vitamin intake. It can also be used to monitor dietary compliance in certain medical conditions or research studies.

How the Test Works

You’ll keep a detailed record of all foods and beverages containing niacin (found in meats, whole grains, nuts, and fortified cereals) for 24 hours. Your sample is typically a 24-hour urine collection, which is then analyzed to estimate total niacin intake.

Sample Collection and Preparation

You’ll collect all urine produced in a 24-hour period in a special container. This includes waking up, urinating, and finishing the collection before bedtime. The sample is sent to the lab for analysis.

What to Expect During the Test

No special preparation is needed beyond keeping a food diary. You may need to adjust your fluid intake slightly to ensure adequate urine volume, but avoid excessive diuretics or caffeine.

Reference range

Premenopausal: 20-400 pg/mL; Postmenopausal: <30 pg/mLN/A

Specimen: serum

No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Vitamin B3 Intake (24h)

Frequently asked questions

What does a low or high result mean?
A low result suggests your diet may not be providing enough niacin, which could contribute to deficiency symptoms. A high result may indicate excessive intake from supplements or certain foods, though this is less common in standard diets.
How often should I get this test?
This test is usually done as a one-time assessment for specific reasons, such as dietary monitoring or research. Your provider will determine if repeat testing is needed based on your symptoms and overall health.
Can I take supplements before the test?
Yes, but inform your provider about any niacin or B-vitamin supplements you’re taking. They may advise adjusting intake temporarily to avoid skewing results.
  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