Though lactose intolerance typically causes symptoms like stomach pain, bloating, and diarrhea, it may also occasionally cause constipation.

Having lactose intolerance can mean living with many uncomfortable symptoms. While you may notice immediate ones like flatulence or diarrhea, it may also cause slower or delayed bowel movements.

Let’s look at the relationship between lactose intolerance and constipation, including how to treat it, when to seek medical care, and more.

Yes. Though it’s not the most common symptom, lactose intolerance may cause constipation in some individuals. According to a 2022 review, constipation may be a symptom of lactose intolerance in about 30% of cases.

Lactose intolerance is a condition that occurs when the body can’t break down a naturally occurring sugar in milk called lactose. Instead, the body ferments the undigested lactose, producing gas and acids in the intestines. This typically leads to issues like flatulence, diarrhea, and stomach pain. However, researchers think that the gas and acids may also sometimes slow down digestion and cause constipation.

Lactose intolerance symptoms typically start between 1 to 2 hours after eating something containing lactose, such as dairy-based milk or yogurt.

Constipation, meanwhile, is a condition that occurs when bowel movements are hard to pass or occur fewer than three times a week.

An estimated two-thirds of the world can’t digest lactose well — so if you’re one of them, you’re not alone.

Reducing or eliminating lactose from the diet is the primary way to manage lactose intolerance symptoms like constipation, but that doesn’t mean you have to forego ice cream or other favorites altogether.

Here are some ways to successfully manage and prevent the issue:

  • Dietary adjustments: Reducing or even completely eliminating lactose from the diet may help resolve symptoms. According to 2019 research, most people with lactose intolerance can tolerate about 12 g (grams) of lactose (about 250 mL (milliliters) of milk) without issues. You may be able to consume more if the meal has other elements or you spread out the consumption throughout the day.
  • Medication: Many people take over-the-counter (OTC) lactase enzyme supplements like Lactaid to prevent and relieve symptoms. These medications are intended to be taken just as you eat dairy to help your body break down the lactose. Taking them too early or too late may make them ineffective.
    • If you’re already experiencing constipation, you may also discuss taking an OTC laxative, stool softener, or prescription-strength laxative with your doctor.
  • Probiotics and prebiotics: There’s an increasing amount of research supporting the use of probiotics to improve lactose indigestion. In a 2023 review of several studies, researchers found that the probiotic Bifidobacterium and the prebiotic galacto-oligosaccharides (GOS), in particular, may reduce lactose intolerance symptoms and can have a favorable effect on gut health overall.

Other ways to treat constipation in general include:

  • Fiber: Increasing your fiber intake is one of the best ways to reduce constipation. In general, a diet high in vegetables, fruits, and legumes will typically contain sufficient fiber.
  • Hydration: Drinking plenty of water can help reduce constipation symptoms.
  • Exercise: Exercising regularly can also help get your system moving.
  • Relaxation: Since constipation is often linked to stress, relaxing your body may help soothe symptoms. Breathing techniques, meditation, yoga, therapy, or simply resting may help aid in healthy, normal digestion.
  • Supplements: Magnesium citrate is a mineral supplement that helps water collect in the intestines, softening the stool and aiding digestion. Psyllium husk is also a natural fiber supplement that can help promote regular bowel movements.

If you don’t see any improvements after at-home treatments, make sure to see a doctor to discuss clinical options for treatment.

Did you know?

When adding a fiber supplement to your diet, you need to time it right. High amounts of fiber in your stomach can prevent proper absorption of medications, vitamins, or other supplements.

Talk with a healthcare professional to determine the best time to take a fiber supplement if you rely on other medications.

If symptoms don’t resolve after a week, speak with a doctor. You may have another issue like IBS that requires treatment. Your doctor can also give you a lactose breath test to determine whether you have lactose intolerance.

You should also always visit a doctor if constipation symptoms don’t resolve within about 7 days or if you experience constipation coupled with any of the following:

Lactose intolerance may sometimes lead to constipation, though symptoms like bloating, gas, and diarrhea tend to be much more common.

Managing dairy-related constipation typically involves reducing lactose intake, but you may also use at-home treatment to help reduce or relieve constipation symptoms. Taking lactase enzyme supplements, increasing fiber and fluid intake, and making other healthy lifestyle changes may help.

If symptoms don’t improve within a week, speak with a doctor.