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13C-urea breath test Pregnancy: SPC 4.6 Pregnancy and breastfeeding: the endogenous production of urea amounts to 25 - 35 g/day, so it is unlikely that the dose of 50 mg urea should cause any adverse effects on pregnancy and lactation. The Diabact UBT test is not expected to be harmful during pregnancy or to the health of the foetus/newborn child. Diabact UBT can be used during pregnancy and lactation.

Urea (13C)

Brand names: Diabact UBT, Helicobacter Test INFAI

Urea labelled with the stable carbon-13 isotope is a diagnostic agent used in the urea breath test to detect Helicobacter pylori infection in the stomach.

Adult dose

Dose: In vivo diagnosis of gastroduodenal primary or remaining Helicobacter pylori infection (diagnostic use only; 13C-urea breath test). Product: Diabact UBT 50 mg tablet (each tablet contains 13C urea 50 mg, enriched stable isotope). One tablet as a single dose at one test occasion. The patient should fast for at least six hours preceding the test. An initial breath test sample is taken, after which the tablet is swallowed whole with a glass of water. A breath sample is taken after ten minutes.
Route: Oral (tablet swallowed whole with a glass of water)
Frequency: Single dose at one test occasion
SCOPE: these figures are the UK SPC for ONE product only, Diabact UBT 50 mg tablets (Laboratoires Mayoly Spindler, PL195490007). This page also names Helicobacter Test INFAI and describes a citric acid drink regimen; those are other 13C-urea breath test products with their own SPCs, and their doses, test meals and sampling times are NOT covered here and must not be inferred from this card. The SPC states: 'This medicinal product is for diagnostic use only.' It also says to follow the instructions for use in section 6.6, which was not retrieved. The tablet must be swallowed whole: if the patient chews the tablet, the test must be performed again as the risk of false positive results increases; a new test may be performed the following day. TIMING OF THE TEST: the test must not be used until at least four (4) weeks after systemic antibacterial therapy and at least two (2) weeks after the last dose of acid antisecretory agents (especially important after eradication therapy). INTERPRETATION: a positive urea breath test alone does not clinically confirm that eradication therapy is indicated; alternative diagnosis with invasive endoscopic methods might be indicated to examine for other complicating conditions, e.g. gastric ulcer, autoimmune gastritis and malignancies. The SPC prints no maximum dose, and no repeat-dose schedule beyond the repeat test noted above.

Dose adjustments

Renal

No renal dose adjustment is stated in the SPC (single diagnostic dose).

Hepatic

No hepatic dose adjustment is stated in the SPC (single diagnostic dose).

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via MHRA Products — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • Documented or suspected gastric infection that might interfere with the urea breath test (the test must not be used)
  • Hypersensitivity to the active substance or to any of the excipients listed in section 6.1
  • Not recommended: there are insufficient data to recommend use in patients with partial gastrectomy and in patients younger than 18 years (SPC 4.4)

Side effects

  • Isolated reports of stomach pain, fatigue and distortion of the sense of smell (parosmia) in one clinical trial (SPC 4.8)

Interactions

  • Antibiotics: the validity of the test result may be affected if the patient is currently being treated with antibiotics or has completed a course; suppression of H. pylori may lead to false negative results; do not use the test until at least 4 weeks after systemic antibacterial therapy
  • Proton-pump inhibitors and other acid antisecretory agents: validity may be affected; do not use the test until at least 2 weeks after the last dose
  • Results may in general be affected by all treatments interfering with H. pylori status or urease activity

Monitoring

  • The patient must fast for at least six hours before the test
  • Breath samples: one before the tablet is swallowed and one ten minutes afterwards
  • If the tablet is chewed, repeat the test (a new test may be performed the following day)
  • A positive test alone does not confirm that eradication therapy is indicated; consider endoscopic assessment for other conditions (gastric ulcer, autoimmune gastritis, malignancy)

Clinical monograph

How it works

If H. pylori is present, its urease enzyme hydrolyses the ingested labelled urea into ammonia and labelled carbon dioxide, which is absorbed and exhaled and then measured in breath samples.

Prescribing in practice

  • The test can give false-negative results if the patient has recently taken proton pump inhibitors, antibiotics or bismuth, so these should be stopped for the recommended washout period beforehand.
  • It is taken after fasting, usually with a citric acid drink to delay gastric emptying and improve test performance.
  • It is a purely diagnostic, non-radioactive agent suitable for confirming eradication after treatment as well as initial diagnosis.

Monitoring

No drug monitoring is required; the test outcome is determined by comparing labelled carbon dioxide in pre- and post-dose breath samples.

Counselling the patient

  • Avoid eating before the test and follow the fasting instructions you are given.
  • Tell the team if you have recently taken acid-suppressing medicines or antibiotics, as these can affect the result.

Evidence & guidelines

The carbon-13 urea breath test is endorsed by NICE as a non-invasive method for diagnosing H. pylori and confirming eradication.

Reference: NICE CG184; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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