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Prescribed Oral Iron Absorption Study (Iron Tolerance Test)

Published: August 9, 2026Updated: August 17, 2026

This test measures how well your body absorbs iron after taking a dose of iron by mouth. It helps assess iron deficiency or malabsorption issues.

Quick summary

["This test checks if your body efficiently uses iron from food or supplements."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
72063-1
Short code
TYPEORALIRONPRESCRIBED
Synonyms
—
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
60
Ref high
170
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
esrd
CPT
83540
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

What Does This Test Measure?

The test involves taking a specific dose of iron orally and measuring how much of it enters your bloodstream over time. This helps determine if your intestines are absorbing iron properly.

Why Might Your Doctor Order This Test?

Your doctor may recommend this test if you have symptoms like fatigue, pale skin, or unusual tiredness, or if lab results suggest low iron levels despite normal dietary intake.

How Is the Test Performed?

You’ll take an iron supplement by mouth on the day of the test. Blood samples are drawn at scheduled intervals to measure iron levels in your bloodstream.

What to Expect Before the Test

No special preparation is needed, but inform your doctor about any medications you’re taking, especially those affecting iron absorption.

Reference range

NCBI: Serum Iron Male 65-180; Female 50-170 µg/dLN/A

Specimen: serum

Fasting for 12 hours preferred. Iron supplements should be stopped 24 hours before if possible.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

This test is crucial for diagnosing conditions like iron deficiency anemia or celiac disease, which can impair iron absorption. Low absorption may indicate underlying gastrointestinal issues or malabsorption syndromes.

Short name

Iron Tolerance Test

Frequently asked questions

Why did my doctor order this test?
Your doctor may suspect poor iron absorption due to symptoms like fatigue, weakness, or unexplained anemia, or if previous blood tests showed low iron levels despite normal dietary intake.
What do my test results mean?
Results show how efficiently your body uses iron. Low absorption may indicate conditions like celiac disease, Crohn’s disease, or other gastrointestinal disorders.
Can I take iron supplements before this test?
Avoid taking iron supplements for at least 24 hours before the test to ensure accurate results. Follow your doctor’s instructions for the best outcome.
  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 17, 2026. · Read our editorial policy