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Breath Hydrogen to Glucose Ratio (24-hour)

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

This test measures the relationship between hydrogen gas in your breath and glucose levels over a 24-hour period, often used to assess how well your body metabolizes carbohydrates.

Quick summary

["This test helps evaluate carbohydrate metabolism and may be used in diabetes management or metabolic studies."]

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

Key facts at a glance

LOINC
16996-1
Short code
Breath H2 pre Glc
Synonyms
Breath H2 pre Glc
Category
glucose
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
true
Population
adult
Sex
all
Age range
18–65 years
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?

Breath hydrogen (H₂) is produced naturally when certain bacteria in your gut break down undigested carbohydrates. The test tracks how your body processes glucose by comparing breath hydrogen levels to glucose metabolism over time. This can help identify issues like malabsorption or metabolic disorders.

Why Might You Need This Test?

Doctors may order this test if you have symptoms of digestive issues (like bloating, diarrhea, or weight changes), unexplained metabolic problems, or if you’re being monitored for conditions like small intestinal bacterial overgrowth (SIBO) or diabetes-related metabolic changes.

How Is the Test Performed?

You’ll breathe into a special device for 24 hours while tracking glucose levels (often via a continuous glucose monitor or self-measured blood glucose). Breath samples are collected at intervals to measure hydrogen levels, and the results are analyzed to compare patterns.

What Are the Possible Results?

Results are interpreted as a ratio or pattern rather than a single number. Abnormal patterns may indicate inefficient glucose metabolism, bacterial overgrowth, or other digestive or metabolic issues that need further evaluation.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Frequently asked questions

What does a high or low ratio mean?
A high ratio of breath hydrogen to glucose may suggest inefficient digestion or bacterial overgrowth in the small intestine, which could interfere with nutrient absorption. A low ratio might indicate normal metabolism, but results should always be reviewed by your healthcare provider.
How often is this test repeated?
The frequency depends on your clinical needs. Your doctor may recommend retesting if symptoms persist or if initial results suggest ongoing issues with glucose metabolism or digestion.
Can lifestyle changes affect this test?
Yes, diet, exercise, and medications can influence breath hydrogen levels. Avoiding certain foods (like high-fiber or fermentable carbohydrates) for a few days before testing may help provide clearer results. Always follow your provider’s specific 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