Overview

Limosilactobacillus reuteri (L. reuteri) is a probiotic bacteria that is available over the counter as a supplement. It is often used for certain types of diarrhea. It may also be used to improve gut and immune health, but its benefits are not well defined. Common side effects include gas and upset stomach. In rare cases, it may cause an infection in some people who are at high risk for infections. Before taking L. reuteri, make sure to tell your health care provider about any health conditions you have or medicines you are taking.

Uses

What is Limosilactobacillus reuteri (L. reuteri) used for?

L. reuteri is a probiotic. It is commonly used for certain types of diarrhea. It is also used to improve gut health and strengthen the immune system, but its benefits for these uses are not well defined.

L. reuteri may also be used for other conditions as determined by your health care provider.

L. reuteri is available as a dietary supplement in various strengths and dosage forms. Some dietary supplements that contain L. reuteri also contain many other ingredients, including other probiotics.

Note: The Food and Drug Administration (FDA) has not reviewed L. reuteri products for safety and effectiveness. Learn more about dietary supplements here.

How does L. reuteri work (mechanism of action)?

L. reuteri is a species of bacteria. It is a type of probiotic, which means it is a live microbe that may provide health benefits in some people.

Your gut is home to millions of different microbes, which make up your gut microbiome. L. reuteri is naturally found in your gut. You can also get L. reuteri from dietary supplements and some of the foods that you eat, such as kefir, sauerkraut, kimchi, sourdough bread, and certain types of yogurt.

L. reuteri makes a substance called lactic acid. Lactic acid can help improve the health of your microbiome by reducing the amount of bad bacteria and increasing the amount of good bacteria. When your gut microbiome is healthy, it can improve your ability to digest foods and resist infections. But it is not clear if L. reuteri is helpful for any health problems in adults. In children, it may help the gut recover more quickly from diarrhea that is caused by an infection. It may also help reduce the symptoms of colic in some babies.

Taking L. reuteri increases the levels of this bacteria in your gut. This may help improve the health of your microbiome. But there are many factors that can affect whether a probiotic survives in your gut. When you take L. reuteri by mouth, it may not always survive long enough to grow and multiply in your gut. As a result, its benefits for gut health are not well defined and may be different for each person.

How should I store L. reuteri?

You should store L. reuteri according to the product label. Most dietary supplements should be kept in a cool, dry location that is out of the reach of children and pets and not in direct sunlight.

Side Effects

What are the most common side effects of L. reuteri?

The most common side effects of L. reuteri are listed below. These side effects may vary depending on the dose you are taking or the specific product you are using. Tell your health care provider if you have any of these side effects that bother you.

• Gas
• Upset stomach

There may be other side effects of L. reuteri that are not listed here. Contact your health care provider if you think you are having a side effect of a supplement. In the U.S., you can report side effects to the FDA at www.safetyreporting.hhs.gov or by calling 888-SAFEFOOD (888-723-3366). In Canada, you can report side effects to Health Canada at www.health.gc.ca/medeffect or by calling 866-234-2345.

What are the serious side effects of L. reuteri?

While less common, the most serious side effects of L. reuteri are described below, along with what to do if they happen.

Severe Allergic Reactions. L. reuteri may cause allergic reactions, which can be serious. Stop taking L. reuteri and get help right away if you have any of the following symptoms of a serious allergic reaction.

• Breathing problems or wheezing
• Racing heart
• Fever or general ill feeling
• Swollen lymph nodes
• Swelling of the face, lips, mouth, tongue, or throat
• Trouble swallowing or throat tightness
• Itching or skin rash
• Bumps on the skin called hives that can be red, pink, white, or brown depending on your skin tone
• Nausea or vomiting
• Dizziness, feeling lightheaded, or fainting
• Stomach cramps
• Joint pain

Serious Infections. In very rare cases, some people who take probiotics such as L. reuteri can get a serious infection. This happens when L. reuteri moves into a part of the body where it is not supposed to be, such as your blood. This is most likely to happen in people who are very sick or who have very weak immune systems, such as people with cancer or who are receiving chemotherapy. Call your health care provider right away if you have any of the following symptoms.

• Fever, sweats, chills, or muscle aches
• Tiredness
• Shortness of breath
• Fast heartbeat

Precautions

Who should not use L. reuteri?

Allergies to Ingredients. People who are allergic to any of the following should not take L. reuteri.

• L. reuteri
• Limosilactobacillus reuteri
• Any of the ingredients in the specific product

Your pharmacist can tell you all of the ingredients in the specific L. reuteri products they stock.

What should I know about L. reuteri before using it?

L. reuteri is a dietary supplement. It cannot be marketed to treat or cure a disease.

Read and follow the directions on the specific product you are taking, or take it as recommended by your health care provider.

Keep L. reuteri out of the reach of children.

Premature infants can be at greater risk of side effects from probiotics such as L. reuteri. Talk to your health care provider about the risks if your infant was born prematurely.

The full name for L. reuteri, Limosilactobacillus reuteri, has only been around since 2020. Before then, this species of bacteria was called Lactobacillus reuteri. You may still see both of these names on product labels. These are the same species of bacteria.

Probiotics such as L. reuteri are usually measured in colony forming units (CFUs). Each CFU is equal to one living bacteria. The number of CFUs listed on the product label tells you how many living bacteria should be in that product on the day that it expires. Since bacteria slowly die off over time, the number of living bacteria in the product may be higher than the amount on the label.

Many probiotic products contain multiple different species of microbes. Different microbes can have different effects in the body. It is important to read the product label closely to understand which species of bacteria are in that product.

L. reuteri is a species of bacteria. Within that species are many different strains. Each strain of L. reuteri may have slightly different effects in the body. This means that some strains of L. reuteri may have certain effects that other strains do not. If the product you are using contains a specific strain, it should be listed on the product label as the string of numbers or letters that come after “L. reuteri.” If you switch to a different strain of L. reuteri, it may not have the same effects or side effects. Talk to your health care provider if you have questions or concerns.

Some probiotic products have been found to contain other microbes that are not listed on the label and that may cause serious health problems. The FDA has not tested L. reuteri products to confirm that they contain the ingredients stated on their labels. Some dietary supplements have been tested by third-party organizations to confirm that they contain the ingredients listed on their labels and do not contain any harmful chemicals. Learn more about how to choose a safe dietary supplement product here.

What should I tell my health care provider before using L. reuteri?

Tell your health care provider about all of your health conditions and any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. This will help them know if L. reuteri is right for you.

In particular, make sure that you discuss any of the following.

Central Line or Port.A central venous catheter (central line) or port is a small tube placed into a vein that can be used to give medicines and fluids directly into the vein (intravenously, or IV). These tubes can become infected by microbes, including probiotics. If you have a central line or port, speak with your health care provider before taking L. reuteri.

Other Current and Past Health Conditions.Tell your health care provider if you have any of the following.

• An autoimmune condition
• Cancer
• Immune problems, such as a weak immune system

Other Medicines and Supplements.L. reuteri may interact with other medicines and supplements. Before taking L. reuteri, tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using. See the Interactions section for more details.

Pregnancy. It is not known if or how L. reuteri could affect pregnancy or harm a fetus. Tell your health care provider if you are pregnant or plan to become pregnant.

Breastfeeding. It is not known if L. reuteri passes into breast milk. Tell your health care provider if you are breastfeeding or plan to breastfeed.

Interactions

Does L. reuteri interact with foods or drinks?

There are no known interactions between L. reuteri and foods or drinks.

It is unknown if drinking alcohol will affect L. reuteri.

Does L. reuteri interact with medicines (drug interactions)?

Always tell your health care provider about any prescription or over-the-counter (OTC) medicines, vitamins/minerals, herbal products, and other supplements you are using.

In particular, make sure that you discuss if you are using any of the following before taking L. reuteri.

• A medicine that suppresses the immune system
• An antibiotic, which is used to treat certain bacterial infections
• Chemotherapy, which is used to treat certain cancers

The interactions between L. reuteri and medicines are not fully understood. As with most dietary supplements, the research on drug interactions with L. reuteri is incomplete. Always check with your health care provider before taking L. reuteri with any medicines.

Dosing

What should I do if I accidentally use too much L. reuteri?

If you or someone else has used too much L. reuteri, get medical help right away, call 911, or contact a Poison Control center at 800-222-1222.

L. reuteri products may contain many different ingredients, including other probiotics. Read the product label closely and speak with a health care provider about how to take L. reuteri safely. Do not take double or extra doses, even if you miss a dose.