13c Urea and Citric Acid (Oral)

13C urea and citric acid are used to treat H. pylori, a strain of bacteria typically contracted in the stomach during childhood.


The medicines 13C urea and citric acid form the basis of the Exalenz BreathID® breath test, which uses before and after breath samples to diagnose H. pylori infections.

You take both medicines orally, so the test is not painful. Exalenz BreathID® is classified as a non-invasive diagnostic test. During the test, your doctors will analyze two different breath samples, one taken before and one after you ingest before and after taking 13C-enriched urea. In the presence of H. pylori bacteria, the 13C urea breaks down into carbon dioxide. By measuring the amounts of carbon dioxide before and after you take the medicines, your doctor can determine whether you have the H. pylori bacteria in your stomach.

In order to make a better diagnosis, your doctor takes the breath test by collecting samples with the BreathID® Hp device. To perform the test, the doctor will ask you to drink a solution containing the 13C-urea tablet and citric acid powder. Usually, you are given no more than two hours to finish the solution. Then, for the breath sample, you simply breathe normally into the cannula of BreathID® Hp device when the test is underway.

Since there is no other diagnostic test that has been found to be effective, these medicines play a vital role in determining the cause of a patient’s stomach pain and discomfort so that it can be properly treated.

Preparation for the test:

  • Don’t eat for one hour prior to consuming the 13C-urea tablet and citric acid powder solution.
  • Ensure that the mixed solution doesn’t have large particles after you mix it. If it does contain large particles after five minutes of mixing, don’t use it. Instead, get a new kit.

Conditions Treated

These medicines are used to detect:

  • H. pylori bacteria
  • Gastritis
  • Peptic ulcers

Type of Medicine

  • Diagnostic

Side Effects

While taking this and other medications, you may experience undesirable impacts. These medications can cause one or more of the following side effects. However, you may not experience any of them at all. Further, just because you have one of these conditions doesn’t mean you will get any of the others.

Check with a medical professional immediately if any of the following occur after you take the medications:

  • Swollen hands, face, lips, eyelids or feet
  • Faster heartbeat than usual
  • Fever
  • Irritation, hives, itching, or rash
  • Hoarseness
  • Stiffness, swelling or joint pain
  • Reddened skin
  • Tightness in the chest, troubled breathing or swallowing

This list may not be complete. Check with a doctor or nurse if you experience any unusual symptoms after taking 13C urea and citric acid. Another rule of thumb is to monitor whether symptoms worsen. Once you begin to have trouble breathing, call for help immediately and go to the nearest hospital if symptoms worsen further.

If you wish to report new side effects to the FDA, call them at 1-800-FDA-1088.


In order to access 13C urea and citric acid, you need a prescription, which is available by:

  • Tablet
  • Powder


While medicines are meant to help you, there are certain types of medications that should not be mixed. Also, some physical conditions prevent you from using specific medicines. The same is true to 13C urea and citric acid.

When you get an unusual reaction, you may need to change the dosage or stop using your prescriptions or over-the-counter medicine. Luckily, the diagnostic test is a one-time event, so you shouldn’t have to worry about long-term reactions. Nevertheless, tell your doctor about any prescriptions you are taking prior to undergoing the test. This way she can advise you whether or not to make any changes in the days leading up to the Exalenz BreathID® breath test.

It is not advised to take or use certain medicines or eat some foods that could interact with these medications adversely. Avoid alcohol and tobacco products, since they can interact with this treatment. If you have specific concerns regarding food, alcohol or tobacco used in conjunction with these medications, feel free to consult a medical professional so that you can put your mind at ease.


Since these medicines are used for a voluntary diagnostic test, they should be taken with discretion and only after consulting closely with your doctors. Weigh the perceived benefit of the test against all possible risks. Below, find warnings for certain conditions that may impact the advisability of taking this test.


Share with your medical team any allergic reactions to not only 13c urea and citric acid, but any other medications as well. Even if it seems unrelated, it’s important to disclose any predilection for allergic reactions to medications, so that your doctor can be prepared. Further, share other types of allergies, including dyes, foods, animals or preservatives. Ask the doctor for the ingredients and a fact sheet on the 13c urea and citric acid medication provided.


Although h. pylori is contracted during childhood, the diagnostic test is not recommended for children. As of yet, further studies are required to fully understand the impacts of 13C urea and citric acid on children. The relationship of age and interactions with these medicines has not been established, nor has the efficacy of the diagnostic test on children.


Similar to children, no age-related data is available for geriatric patients relating to the successful results of the 13C urea and citric acid test.

Pregnancy and Breastfeeding

It isn’t recommended that pregnant women undergo the diagnostic test. Animal studies indicate that there is an adverse risk to pregnant women that outweighs the possible benefits. There is not enough compelling data to determine the impact of the medicines or the effectivity of the diagnostic test when performed on pregnant women.

Similarly, breastfeeding women should refrain from taking these medications unless there is a very compelling reason to undergo the diagnostic test. It’s not worth the risk to your infant if you can wait until you are done breastfeeding. Again, the lack of adequate studies to determine risks during breastfeeding makes this an unnecessary risky procedure.

Other Medical Problems

If you have any of the following medical problems, they can impact the efficacy of the diagnostic test. Tell your doctor if have any of the following conditions. Refer to the recommendations given for each.

Gastrectomy (surgery to remove the stomach).

  • Recommendation: Do not undergo the diagnostic test

Achlorhydria. The condition in which your stomach lacks acid, which can interfere with the test results.

  • Recommendation: Do not undergo the diagnostic test.

Phenylketonuria. Be aware that 13c urea and citric acid have phenylalanine, which makes it worse.

  • Recommendation: Follow the advice of your doctor.


  • Recommendation: Wait two weeks prior to undergoing the test.

Proton pump inhibitors (omeprazole, lansoprazole).

  • Recommendation: Wait two weeks prior to undergoing the test.


Store the 13c urea and citric acid at 25 degrees Celsius (77 degrees Fahrenheit). During travel, the tolerance is 15 to 30 degrees Celsius (59 to 86 degrees Fahrenheit).

Note that some components of the test kit may have expiration dates. For example, the 13C-urea tablet and the citric acid powder will each come with expiration information. If the expiration date has passed, do not use the kit under any circumstances. These will have unique labels with separate expiration dates. However, if either is expired, it isn’t recommended to use the kit.


13c urea and citric acid is the most effective way to detect h. pylori bacteria in the stomach. Despite the risk factors involved, excluding notable exceptions, this medicine is recommended for the Exalenz BreathID® breath test that can be used to determine whether you have the bacteria.

The health benefits of this test include understanding certain conditions that can result from the infection, such as:

  • Peptic ulcer
  • Gastritis

Peptic ulcers form in the lining of your stomach or the small intestine (duodenum). The h. pylori infection can aggravate the stomach lining, making it easier to develop ulcers. If you have an H. pylori infection, it’s highly likely you will develop gastritis, which is simply an inflammation of your stomach lining. These conditions cause a great deal of pain and discomfort and can make eating difficult. So, if detecting the h. pylori bacteria can facilitate the diagnosis and treatment of this issues, it is worth minor side effects.

The test itself is not difficult, is non-invasive and bears little risk to the vast majority of individuals. Pregnant and nursing mothers, children and elderly patients and people suffering from certain conditions should postpone the test until their condition ends or is resolved.

Last Reviewed:
December 10, 2017
Last Updated:
February 09, 2018
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