u/ipsmakkar

Disclosure upfront: I’m the co-founder of Aloft MedTech, an Indian company that manufactures 13C urea breath test systems (ALOFT-UBT). This post is general education, not medical advice — always work with your doctor. Happy to answer technical questions in the comments.
The problem I keep seeing
A lot of people first get tested for H. pylori with a blood (antibody/serology) test. The catch: antibodies can stay positive for months or even years after the bacteria are gone. So a blood test can’t tell you whether you have an active infection right now — and it’s useless for confirming eradication after antibiotics. That’s why major guidelines (Maastricht VI, ACG) recommend the urea breath test (UBT) or the stool antigen test for both diagnosis and test-of-cure.
How the 13C urea breath test works
It’s genuinely elegant science:
1. You fast for 4–6 hours, then give a baseline breath sample.
2. You drink a small dose of urea labelled with carbon-13 (¹³C) — a non-radioactive, naturally occurring isotope. (Not to be confused with the older ¹⁴C version, which uses a radioactive tracer.)
3. If H. pylori is living in your stomach, its urease enzyme splits that urea into ammonia and ¹³CO₂. The labelled CO₂ enters your bloodstream and comes out in your breath.
4. About 15–30 minutes later you give a second sample. The analyser measures the shift in the ¹³C/¹²C ratio (the “delta over baseline”). Above the cut-off = active infection.
No bacteria → no urease → no signal. That’s why sensitivity and specificity are both around 95%, and why it’s widely considered the gold-standard non-invasive test for active infection. Because ¹³C is a stable isotope (zero radiation), it’s safe for children and during pregnancy, and fine to repeat.
Prep mistakes that cause false negatives
Most “wrong” results come from prep, not the test:
• PPIs (omeprazole, pantoprazole, esomeprazole, rabeprazole…): stop about 2 weeks before. PPIs suppress the bacteria enough to hide it.
• Antibiotics or bismuth: none in the 4 weeks before testing.
• Test-of-cure timing: wait at least 4 weeks after finishing eradication therapy before retesting.
• Fasting: 4–6 hours before the test.
(H2 blockers like famotidine are generally less of an issue than PPIs, but follow your lab’s instructions.)
Quick comparison
• Endoscopy + biopsy — makes sense when your doctor needs to look inside anyway (ulcers, alarm symptoms); invasive and costly as a pure H. pylori check.
• Stool antigen — accurate for active infection and test-of-cure; sample collection and handling matter.
• 13C UBT — accurate for active infection and test-of-cure; non-invasive, and many centres run the whole thing, sample to result, within the hour.
• Blood antibody test — tells you about past exposure only. Never use it to confirm eradication.
If you’re in India
Serology is unfortunately still bundled into a lot of lab packages here, so ask specifically for a 13C UBT or stool antigen test. Availability has improved a lot — indigenous, CDSCO-licensed systems like ALOFT-UBT are now installed at hospitals and diagnostic centres across the country, so you no longer need to hunt for a metro speciality lab.
If anything above is unclear, ask below — I spend my working life on this exact test and I’m glad to go as deep into the science as you want.

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Disclosure upfront: I’m the co-founder of Aloft MedTech, an Indian company that manufactures 13C urea breath test systems (ALOFT-UBT). This post is general education, not medical advice — always work with your doctor. Happy to answer technical questions in the comments.
The problem I keep seeing
A lot of people first get tested for H. pylori with a blood (antibody/serology) test. The catch: antibodies can stay positive for months or even years after the bacteria are gone. So a blood test can’t tell you whether you have an active infection right now — and it’s useless for confirming eradication after antibiotics. That’s why major guidelines (Maastricht VI, ACG) recommend the urea breath test (UBT) or the stool antigen test for both diagnosis and test-of-cure.
How the 13C urea breath test works
It’s genuinely elegant science:
1. You fast for 4–6 hours, then give a baseline breath sample.
2. You drink a small dose of urea labelled with carbon-13 (¹³C) — a non-radioactive, naturally occurring isotope. (Not to be confused with the older ¹⁴C version, which uses a radioactive tracer.)
3. If H. pylori is living in your stomach, its urease enzyme splits that urea into ammonia and ¹³CO₂. The labelled CO₂ enters your bloodstream and comes out in your breath.
4. About 15–30 minutes later you give a second sample. The analyser measures the shift in the ¹³C/¹²C ratio (the “delta over baseline”). Above the cut-off = active infection.
No bacteria → no urease → no signal. That’s why sensitivity and specificity are both around 95%, and why it’s widely considered the gold-standard non-invasive test for active infection. Because ¹³C is a stable isotope (zero radiation), it’s safe for children and during pregnancy, and fine to repeat.
Prep mistakes that cause false negatives
Most “wrong” results come from prep, not the test:
• PPIs (omeprazole, pantoprazole, esomeprazole, rabeprazole…): stop about 2 weeks before. PPIs suppress the bacteria enough to hide it.
• Antibiotics or bismuth: none in the 4 weeks before testing.
• Test-of-cure timing: wait at least 4 weeks after finishing eradication therapy before retesting.
• Fasting: 4–6 hours before the test.
(H2 blockers like famotidine are generally less of an issue than PPIs, but follow your lab’s instructions.)
Quick comparison
• Endoscopy + biopsy — makes sense when your doctor needs to look inside anyway (ulcers, alarm symptoms); invasive and costly as a pure H. pylori check.
• Stool antigen — accurate for active infection and test-of-cure; sample collection and handling matter.
• 13C UBT — accurate for active infection and test-of-cure; non-invasive, and many centres run the whole thing, sample to result, within the hour.
• Blood antibody test — tells you about past exposure only. Never use it to confirm eradication.
If you’re in India
Serology is unfortunately still bundled into a lot of lab packages here, so ask specifically for a 13C UBT or stool antigen test. Availability has improved a lot — indigenous, CDSCO-licensed systems like ALOFT-UBT are now installed at hospitals and diagnostic centres across the country, so you no longer need to hunt for a metro speciality lab.
If anything above is unclear, ask below — I spend my working life on this exact test and I’m glad to go as deep into the science as you want.