What Does It Mean to Be Lactose Intolerant?

If you love eating an ice cream cone but loathe how you feel afterward, you might be lactose intolerant.

When it’s been a long day, pizza’s an easy dinner. After a few cheesy slices, your stomach starts to gurgle. Maybe it’s the grease or the heaviness of the pizza — or maybe it’s something else, like dairy intolerance.

What is lactose intolerance?

“When you’re lactose intolerant, your digestive system doesn’t produce enough of the enzyme needed to break down lactose, a sugar in dairy products,” says Grace Guerrier, MD, internal medicine doctor at Geisinger. Those undigested dairy products may give you a serious case of indigestion.

Symptoms of lactose intolerance

Besides a stomachache, you might also have:

Bloating
Gas
Diarrhea
Nausea

“Symptoms can come on quickly, within a few hours after eating dairy products,” Dr. Guerrier says.

The intensity of your symptoms depends on how much you eat — and how much digestive enzyme your body makes. You can have mild or severe symptoms.

More severe symptoms can also point to a dairy allergy. Although they’re similar, they have some key differences.

“A dairy allergy causes an immune reaction from coming into contact with dairy products, whereas lactose intolerance is a digestive issue,” says Dr. Guerrier.

An allergic reaction to dairy can trigger red-flag symptoms that include:

Hives
Tingling or itching in lips or mouth
Vomiting
Swelling of the tongue, lips or throat
Shortness of breath

These can be signs of anaphylaxis, which comes on fast and is life-threatening. Call 911 or head to the nearest emergency room if you develop any of these severe symptoms.

How is lactose intolerance diagnosed?

If you have symptoms of lactose intolerance, talk to your healthcare provider. To make a diagnosis, they may order tests including:

Hydrogen breath test

During this test, you’ll breathe into a device measuring your hydrogen levels. Then you’ll drink a liquid containing lactose. After drinking it, you’ll breathe into the device again every few minutes for a few hours. Your provider will ask you about any digestive symptoms you have, like gas, bloating or an upset stomach. When the test is over, your provider will measure hydrogen levels to determine your lactose intolerance.

Glucose blood test

Before your blood is drawn, you’ll drink a liquid that contains a lot of lactose. A few hours later, a technician will draw blood to check your glucose levels. “If they don’t go up, it means you’re lactose intolerant,” Dr. Guerrier says.

Stool acidity test

This procedure is done only on babies and young children. During this test, your child drinks a liquid containing glucose. After they digest the drink, a technician will examine their stool to determine if it’s acidic. Acidic poop means they’re lactose intolerant.

Living with lactose intolerance

Dairy doesn’t have to ruin your day. With some minor adjustments, you can reduce your symptoms and still enjoy your favorites. Consider these healthy habits:

Switching to low-lactose or lactose-free products
Taking lactase supplements before eating dairy products
Adding fermented or cultured foods to your diet
Filling your plate with calcium-rich foods

You may need calcium and vitamin D supplements if you remove dairy from your diet. If you want to eat a small amount of dairy, eat it with other food, says Dr. Guerrier. Doing so can help your body digest lactose better and lessen any symptoms.

Discuss dairy

Not sure if you’re lactose intolerant? Start by talking to your healthcare provider. They can get you tested — and if you are, they can build a plan to help you feel your best.