Lactase is a digestive enzyme involved in the breakdown of lactose, a sugar found in milk and other dairy products.

During digestion, lactase produced in the lining of the small intestine splits lactose into smaller sugar molecules (known as glucose and galactose) for absorption. People with lactose intolerance are not able to produce enough lactase on their own.

A lack of lactase often causes uncomfortable side effects like diarrhea, bloating, stomach pain, and nausea after consuming dairy. Taking lactase supplements may reduce or prevent many of these symptoms for people with lactase deficiency, lactose intolerance, or other conditions affecting the digestion of lactose.

This article will look at the science behind the uses of lactase, its side effects, and precautions. It will also cover dosage and what to look for when choosing a lactase supplement.

Dietary supplements are not regulated in the United States, meaning the Food and Drug Administration (FDA) does not approve them for safety and effectiveness before products are marketed. When possible, choose a supplement that has been tested by a trusted third party, such as USP, ConsumerLabs, or NSF. However, even if supplements are third-party tested, that doesn’t mean they are necessarily safe or effective in general. It is important to talk to your healthcare provider about any supplements you plan to take and to check in about any potential interactions with other supplements or medications.

Supplement Facts

  • Active Ingredient(s): Lactase enzyme
  • Alternate Name(s): Beta-galactosidase, B-galactosidase, Lactase-phlorizin hydrolase (LPH)
  • Legal Status: Legal for sale over-the-counter (OTC)
  • Suggested Dose: Dosage varies from 2,000 to 9,000 international units (IU)
  • Safety Considerations: Lactase is likely safe for most people to take. Allergic reactions are possible.

Uses of Lactase

Supplement use should be individualized and vetted by a healthcare professional, such as a registered dietitian, pharmacist, or doctor. No supplement is intended to treat, cure, or prevent diseases.

Lactase supplements are mostly used by people who have difficulty digesting lactose found in dairy products. People with lactose intolerance, lactase deficiency, or sensitivity to lactose may benefit from using lactase enzymes.

It's important to note that lactase supplements would not be useful for someone with a milk protein allergy. A milk protein allergy is not the same as lactose intolerance. While a person with lactose intolerance cannot properly digest the sugar in milk (lactose), a person with a milk protein allergy cannot properly digest the proteins in milk (casein and whey).

Although lactase is mostly used to prevent symptoms of lactose intolerance, it has also been studied for its role in bone health.

Lactose Intolerance

While lactase enzymes cannot cure lactose intolerance, they may be able to reduce or eliminate symptoms associated with eating dairy. However, even though scientists agree that lactase supplements are safe, there has not always been a consensus on how well they work.

According to a 2010 study, lactase supplements more effectively alleviated lactose intolerance compared with the probiotic Lactobacillus reuteri. The lactase supplements also reduced key gastrointestinal symptoms, especially gas.

However, a 2014 study reported significant variability in response to lactase supplementation. Of the 96 adults given a lactase supplement, 22% showed complete normalization using the lactose breath test, while 18% were fully non-responsive. The lactose breath test, or hydrogen breath test, measures the presence of hydrogen in breath samples. Hydrogen present in a person's breath signifies that the person may be lactose intolerant.

A recent update from 2021 further indicated that lactase enzyme supplements appear to be an appropriate treatment option for those with lactose intolerance.

It should be noted that many people with lactose intolerance have additional food sensitivities or allergies. For example, people with irritable bowel syndrome (IBS) may find it best to avoid food containing lactose and other aggravating ingredients.

Essentially, other factors may contribute to being unable to metabolize lactose. And despite the positive results for lactase enzymes, it may be necessary for some people to use other treatment options for their lactose intolerance. Work with your healthcare provider to find the best option for you.

Bone Health

Lactase supplements cannot improve bone health directly. However, lactase can help people who are lactose intolerant eat more dairy without the side effects, thereby making it easier to consume adequate amounts of calcium.

Eating enough calcium can help build and maintain healthy bones while reducing the risk of bone loss and osteoporosis.

According to a 2019 study, avoiding or cutting back on dairy due to lactose intolerance can put people at risk for bone loss and fractures (broken bones). This is because they are not getting enough calcium.

It should be pointed out that neither lactose intolerance nor lactase deficiency significantly affects the ability to absorb calcium. Therefore, people who have difficulty digesting lactose can still absorb calcium from dairy products.

Results on whether lactose intolerance leads to osteoporosis have been conflicting.

Despite this, it is recommended that everyone—including those with lactose intolerance—consume three servings of dairy per day. Lactase supplements may be able to help you get there.

Lactase Deficiency

According to a 2019 study, around 70% of the world's population is lactase deficient, with the highest prevalence being among people of East Asian, West African, Arab, Jewish, Greek, or Italian descent.

However, not everyone deficient in lactase has lactose intolerance. A deficiency can mean levels of lactase are lower than normal, but still present. And lactose intolerance only occurs when symptoms like bloating, diarrhea, and abdominal pain appear.

Lactase deficiency can appear over time as you age. It can also be diagnosed during childhood or even at birth. Congenital lactase deficiency (CLD) is a very rare disorder diagnosed in newborns and can lead to malnutrition and poor growth.

It should be noted that lactase deficiency does not always result in lactose intolerance. Sometimes, lactase levels never get low enough to cause lactose intolerance.

What Causes a Lactase Deficiency?

Lactase deficiencies can be genetic, but this is not always the case. There are four possible causes of lactase deficiency, with two being genetics-related.

Two genetic causes of lactase deficiency include:

  • Lactase non-persistence: In a person with lactase non-persistence, their lactase levels will get lower over time, causing a gradual decrease.
  • Congenital lactase deficiency (CLD): With CLD, the small intestines never make enough lactase from birth.

There are also two non-genetic causes of lactase deficiency:

  • Injury to the small intestine: In this case, inflammation, infection, or a disease affecting the intestines, like Crohn's disease, can lead to a decrease in the lactase enzyme.
  • Premature birth: Some babies born early have underdeveloped small intestines that have not had time to produce lactase efficiently. The baby may grow out of this type of lactase deficiency over time.

How Do I Know If I Have a Lactase Deficiency?

A lactase deficiency may cause various symptoms alerting you to a problem.

The severity of your deficiency and the underlying cause may worsen symptoms. For example, a person with lactose non-persistence may tolerate some amounts and types of dairy products without experiencing any symptoms.

However, if you have any of the following symptoms within a few hours after consuming dairy, then it may be time to get an official diagnosis:

To officially diagnose lactose intolerance, a healthcare provider may want to perform various tests, including a physical exam and a hydrogen breath test.

You may risk worsening symptoms if a lactase deficiency or lactose intolerance goes undiagnosed. Excessive diarrhea and vomiting can lead to dehydration, while gas and stomach pain can be highly uncomfortable.

Speak with a healthcare provider if you think you may have a lactase deficiency.

What Are the Side Effects of Lactase?

Lactase supplements are generally considered safe and well-tolerated by most people. Side effects are rare.

If your healthcare provider has recommended that you take lactase supplements, they most likely believe the benefits outweigh any potential risks. Consuming any supplement, including lactase, comes with possible side effects.

Remember to check with your healthcare provider before starting lactase supplements.

Common Side Effects

Side effects of taking lactase supplements are not common. However, this doesn't mean that side effects are not possible at all. It simply means that side effects are rare when taking lactase.

Be sure to take lactase supplements as instructed by your healthcare provider or as listed on the label. Taking supplements incorrectly may increase the risk of side effects.

Severe Side Effects

Although very rare, lactase supplements can trigger an allergic reaction. There have been a few cases of lactase causing a severe reaction that requires emergency care.

In one of these reported cases, a 38-year-old person experienced a severe, whole-body allergy known as anaphylaxis after taking lactase for the first time.

If left untreated, anaphylaxis can lead to shock, coma, respiratory or heart failure, and death.

Call 911 or go to your nearest emergency room if you develop any of the following symptoms after taking a lactase supplement:

  • Hives or rash
  • Shortness of breath or wheezing
  • Dizziness or lightheadedness
  • Rapid heart rate
  • Swelling of the face, tongue, or throat

Verywell / Anastasiia Tretiak​


It's important to speak with a healthcare professional before starting lactase supplements. Lactase supplements may not be suitable for certain people in different life stages, with various health conditions, and those with allergies.

Do not take lactase supplements if you are allergic to any of the active or inactive ingredients.

It is best for people who are pregnant or breastfeeding to speak with a healthcare professional before using lactase supplements. Evidence on whether lactase is safe for these populations is limited, so your healthcare provider may advise against taking it.

Dosage: How Much Lactase Should I Take?

Always speak with a healthcare provider before taking a supplement to ensure that the supplement and dosage is appropriate for your individual needs.

Lactase supplement dosage can vary and may depend on a few factors, such as:

  • The severity of your symptoms
  • The amount of lactose you plan to consume
  • Source and brand of lactase supplements

For example, Lactaid supplements (a lactase supplement brand) contain 9,000 units of the active enzyme, while Lacdigest (another lactase supplement brand) contains just 2,250 units.

Lactase doses can vary from 3,000 to 6,000 international units (IU) taken immediately before a meal containing dairy. You may need a lactase dose outside of this range.

It may be helpful to start at a low dose and gradually increase it until you achieve the desired control. Your healthcare provider should be able to assist you in finding the correct lactase dose for you.

Be sure to follow the directions when taking lactase supplements. It is recommended to take a lactase supplement before consuming dairy products. It may be necessary to take an additional dose of lactase if you plan to eat over a period longer than 20 to 30 minutes (say, at a picnic or banquet).

What Happens If I Take Too Much Lactase?

There is no evidence suggesting lactase and other digestive enzymes can be toxic if too much is taken. Lactase enzymes also do not appear to have a tolerable upper limit level, which is the highest nutrient intake level likely not to cause adverse health effects. This means side effects are unlikely if you take more lactase than recommended.

If you take a higher dose of lactase than usual, then your body will most likely excrete what it doesn't need to use to digest lactose.

Still, taking lactase supplements as instructed is best to keep your risk for side effects low.


Lactase interactions are not well documented. No serious food or drug interactions with lactase have been reported.

Regardless, speak with your healthcare provider before starting lactase, especially if you are taking other medications or supplements.

It is essential to carefully read the ingredient list and nutrition facts panel of a supplement to know which ingredients and how much of each ingredient is included. Please review this supplement label with your healthcare provider to discuss any potential interactions with foods, other supplements, and medications.

How to Store Lactase

Store lactase supplements in a sealed container in a cool, dry place in your home. Don't allow your supplements to be exposed to direct sunlight or become too hot or cold.

It's best to store your supplements in their bottle or container.

Supplements may become inactive after their expiration date. Because of this, you should discard lactase supplements once they become expired.

Similar Supplements

You may be able to use other supplements in place of or in addition to lactase enzymes.

Supplements similar to lactase used by some to treat lactose intolerance include:

  • Probiotics: Various studies have shown that probiotics can help treat lactose intolerance. Probiotics are thought to help in different ways, including decreasing diarrhea, expressing lactase, and changing the pH of your gut.
  • Prebiotics: Evidence of prebiotics for treating lactose intolerance is not as strong as probiotics. However, prebiotics may still be a viable option. In one study, prebiotics improved lactose intolerance symptoms and digestion of lactose.
  • Fermented milk: Drinking fermented milk is associated with increased lactase enzyme activity in the small intestine. Choosing fermented dairy products over nonfermented ones is thought to potentially reduce symptoms of lactose intolerance.

You may be able to use these supplements and other lifestyle changes to treat symptoms of lactose intolerance or lactase deficiency. Collaborate with your healthcare provider to find the best treatment plan for you.

Frequently Asked Questions

  • What do lactase supplements do?

    Lactase supplements like Lactaid contain the digestive enzyme lactase. Your body needs lactase to digest lactose, a sugar found in milk and dairy products. 

    Some people are unable to make enough lactase to effectively digest dairy products, leading to uncomfortable symptoms like diarrhea, bloating, and stomach pain. Supplementing with lactase enzyme helps prevent symptoms of lactose intolerance. 

  • Do lactase enzymes have any side effects?

    Lactase is considered a fairly safe supplement and side effects are not common. Most people who take lactase enzymes will not experience side effects.

    On rare occasions, a very serious allergic reaction known as anaphylaxis can occur after taking lactase. If you develop symptoms such as shortness of breath and swelling of the face, tongue, or throat, call 911 or go to the nearest emergency room.

  • Is it safe to take lactase enzyme every day?

    Yes, it is safe to take lactase enzyme supplements every day, even before every meal.

    Typically, lactase enzymes will be taken before any meal or snack containing dairy. But be sure to use lactase enzymes as directed.

  • I take lactase supplements, but they don't seem to be helping. Why?

    Lactase supplements may not work if you are not taking a high enough dose, if you are consuming more dairy than your body can tolerate (even with supplementation), or are not timing your dose right.

    It is possible that some people may simply need to avoid lactose altogether.

    If you are unable to control your symptoms with lactase supplements, ask your healthcare provider for a referral to a gastroenterologist or allergist for further investigation. You may also want to consider if you are actually lactose intolerant.

    People sometimes diagnose themselves or their children with lactose intolerance when they actually have an allergy to milk.

Sources of Lactase & What to Look For

Lactase is not widely found in food. Typically, your body makes lactase for you. But if you cannot make enough lactase, you may need to use a supplement.

Food Sources of Lactase

While there is some thought that certain foods contain lactase, there is no good evidence to support this claim.

Certain probiotics, like those from lactic acid sources, may increase lactase activity after digestion. However, probiotics may not produce enough lactase to eliminate symptoms of lactose intolerance.

Lactase Supplements

Lactase supplements are sold in many forms, including capsules, chewables, powders, and drops.

Widely available for purchase online, lactase supplements can also be found in various grocery stores, drugstores, and shops specializing in dietary supplements. You do not need a prescription to buy lactase supplements.

The U.S. Food and Drug Administration (FDA) regulates dietary supplements as food, not as drugs. Therefore, the agency doesn't have the authority to approve supplement products for safety and effectiveness. To ensure quality and safety, look for brands certified by an independent, third-party authority, such as the U.S. Pharmacopeia (USP), NSF International, or ConsumerLab.

Lactase is not derived from dairy, so taking supplements is not a concern if you are vegan. However, the coating that makes up some capsules may be made of animal-derived gelatin. If this is a concern for you, look for products labeled as vegan.

Finally, remember to be mindful of your dairy intake if you are lactose intolerant. It is possible to experience side effects from lactose intolerance even when using lactase supplements.


Lactase is a digestive enzyme made by the body to break down the lactose found in dairy products. However, many people are unable to produce enough lactase and may need to use a supplement when consuming dairy.

Lactase supplements are generally recognized as safe and come with few potential side effects, precautions, or interactions. Your dose of lactase supplements may depend on the severity of your lactose intolerance symptoms, your dairy intake, and the brand of supplement.

If you are thinking of starting a lactase enzyme supplement, speak with a healthcare provider to find the best dosage and brand for you.

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