Lactose intolerance

Overview

Lactose intolerance is when your body cannot properly digest lactose, a natural sugar found in milk and other dairy products. This happens because your small intestine doesn't make enough lactase, the enzyme that breaks down lactose. Without enough lactase, undigested lactose moves into your large intestine, where it can cause gas, cramping, and diarrhea.

Yes, lactose intolerance is one of the most common digestive problems worldwide. It affects people of all ages, but is especially widespread among adults of Asian, African, Native American, and Hispanic heritage.

Lactose intolerance can occur at any age, but it often develops later in childhood or adulthood. It is more common in people with a family history of lactose intolerance, and in those with certain digestive conditions or after a stomach illness.

Symptoms

Common symptoms

• Bloating and gas
• Stomach cramps and pain
• Diarrhea (often watery and urgent)
• Nausea and sometimes vomiting
• Rumbling sounds in your stomach

Symptoms in children

• Same symptoms as adults — bloating, gas, cramps, diarrhea
• Fussiness and irritability after eating dairy
• Slow weight gain or poor growth in severe cases

Symptoms in older adults

• Same symptoms as younger adults, but may be more pronounced due to age-related decrease in lactase
• May mistake symptoms as a normal part of aging, delaying diagnosis

Causes

Main causes

• Low levels of lactase enzyme in your small intestine — this can be genetic (primary) or occur after an illness or injury to the gut (secondary)
• Some people are born with lactase deficiency from birth (congenital), but this is rare

Risk factors

• Family history of lactose intolerance
• Ethnic background — people of East Asian, West African, Arab, Greek, Italian, and Jewish descent have higher rates
• Age — lactase levels naturally decline as you get older
• Conditions that damage the small intestine, such as celiac disease, Crohn's disease, or a stomach infection

When to see a doctor

See a doctor urgently if:

• If you experience blood in your stool, severe dehydration, or inability to keep fluids down — seek emergency care immediately.

Book a routine appointment if:

• If you have ongoing symptoms like bloating, gas, or diarrhea after eating dairy products for more than a week.
• If symptoms are affecting your quality of life or causing weight loss.

Diagnosis

Your doctor will start by asking about your symptoms, diet, and family history. They may ask you to keep a food diary and try avoiding dairy for a short time to see if symptoms improve.

Tests that may be done

• Hydrogen breath test — you drink a lactose solution, and your breath is tested for hydrogen, which increases when lactose isn't digested properly.
• Lactose tolerance test — a blood test measures your blood sugar levels after drinking lactose.
• Stool acidity test — sometimes used for children; it checks for acid in stool caused by undigested lactose.

What to expect at your appointment

These tests are simple and noninvasive. Your doctor will explain each step and help you prepare — for example, you may need to avoid food and certain drinks beforehand.

Treatment

There is no cure for lactose intolerance, but it can be managed very effectively. The main approach is to limit or avoid foods that contain lactose, while making sure you still get enough calcium and vitamin D from other sources.

Self-care at home

• Read food labels to check for hidden lactose — it's in many processed foods, breads, sauces, and medications.
• Try lactose-free or reduced-lactose milk and dairy products, which are widely available in most supermarkets.
• Eat smaller portions of dairy at one time, and pair dairy with other foods to slow digestion.
• Consider taking lactase enzyme supplements (over-the-counter) just before eating dairy — ask your pharmacist or doctor for advice.

Medical treatments

For some people with underlying conditions like celiac disease, treating the main condition can restore lactase production. Your doctor may also recommend calcium and vitamin D supplements to prevent bone problems, but do not start any supplements without medical advice.

Living with this condition

Living with lactose intolerance means being mindful of what you eat, but most people can still enjoy a varied diet. You'll learn which foods are safe for you and how much lactose you can handle. Over time, this becomes a normal part of your routine.

Lifestyle tips

• Keep a food diary to track how much lactose you can tolerate.
• Choose lactose-free alternatives for milk, yogurt, and cheese.
• Check ingredients on packaged foods — words like milk, whey, curds, and dry milk solids mean lactose is present.
• When eating out, ask your server which dishes are dairy-free or lactose-free.

Diet and exercise

A balanced diet without dairy is possible. Good sources of calcium include broccoli, kale, almonds, fortified plant milks (like soy or oat milk), and canned fish with bones. Vitamin D is important for calcium absorption — you can get it from sunlight and fortified foods. Regular exercise, especially weight-bearing activities like walking, helps keep your bones strong.

Mental health and emotional wellbeing

Some people feel self-conscious about their food choices, especially in social settings. It can be frustrating to worry about symptoms when eating out. But with a little planning, you can enjoy meals with others without anxiety.

Prevention

Primary lactose intolerance (the genetic kind) cannot be prevented. However, you can often prevent symptoms by limiting lactose in your diet. If your lactose intolerance is due to another condition (like celiac disease), treating that condition may help.

Complications

If left untreated

• Calcium deficiency, which can lead to weak bones (osteopenia or osteoporosis)
• Vitamin D deficiency
• Malnutrition in severe cases, especially in children or older adults

Long-term outlook

With proper dietary changes and support from your healthcare team, lactose intolerance is very manageable. Most people live full, healthy lives without significant problems. Your doctor and a dietitian can help you stay well-nourished and comfortable.

Find support

External links open third-party websites. Ruqelo Health is not responsible for external content. Listing an organisation does not imply endorsement.