Lactose intolerance living patient overview

Overview

Lactose intolerance is when your body has trouble digesting lactose, a natural sugar found in milk and dairy products. This happens because you don't have enough lactase, an enzyme that breaks down lactose in your gut.

Yes, it is very common. About 70% of the world's population has some level of lactose intolerance, though it varies by region and ancestry.

It affects people of all ages, but it is most common in adults and in certain ethnic groups, such as people of East Asian, African, Hispanic, and Native American descent. It can also affect children and older adults.

Symptoms

Common symptoms

• Bloating
• Gas (flatulence)
• Diarrhea
• Stomach cramps
• Nausea

Symptoms in children

• Fussiness or irritability after drinking milk
• Bloating and gas
• Loose, watery stools
• Slow growth or weight gain (if severe)

Symptoms in older adults

• Same symptoms as adults, but may be more noticeable due to changes in digestion
• Increased risk of dehydration from diarrhea
• Unintentional weight loss if dairy is avoided without proper nutrition

Causes

Main causes

• A shortage of the enzyme lactase, which is needed to break down lactose in the small intestine
• Primary lactose intolerance: the natural decline in lactase production that happens as you age
• Secondary lactose intolerance: caused by an injury or illness that damages the small intestine, such as a stomach bug, celiac disease, or Crohn's disease
• Congenital lactose intolerance: a rare genetic condition present from birth

Risk factors

• Being of East Asian, African, Hispanic, or Native American descent
• Getting older – lactase levels naturally decrease over time
• Having a digestive disease that affects the small intestine
• Premature birth (babies may not have fully developed lactase production)

When to see a doctor

See a doctor urgently if:

• If you have severe stomach pain that does not go away
• If you see blood in your stool
• If you have signs of dehydration from diarrhea

Book a routine appointment if:

• If you have ongoing bloating, gas, or diarrhea after eating dairy
• If you are losing weight without trying
• If you think your child is not growing well or is always uncomfortable after milk

Diagnosis

Doctors diagnose lactose intolerance by asking about your symptoms and doing simple tests. They may also ask you to try a temporary dairy-free diet to see if symptoms improve.

Tests that may be done

• Lactose tolerance test: you drink a liquid with lactose, then a blood sample is taken to check how your body breaks it down
• Hydrogen breath test: you drink lactose and then breathe into a machine to measure hydrogen gas (a sign of undigested lactose)
• Stool acidity test: used mainly for infants and children to check for undigested lactose in stool

What to expect at your appointment

Your doctor will talk with you about your symptoms and medical history. The tests are simple and not painful. You may be asked to avoid dairy for a short time before testing. Results usually come back within a few days.

Treatment

Treatment focuses on managing symptoms by limiting or avoiding lactose. Most people do not need to cut out all dairy – they can find what amount their body can handle.

Self-care at home

• Try smaller amounts of dairy at a time (for example, a few sips of milk instead of a full glass)
• Eat dairy with other foods to slow digestion and reduce symptoms
• Choose lactose-free or lactose-reduced milk and dairy products
• Try aged cheeses (like cheddar or Swiss) and yogurt, which have less lactose
• Take lactase enzyme supplements before eating dairy (ask your pharmacist for advice)

Medical treatments

If symptoms are hard to manage with diet alone, your doctor may recommend lactase enzyme supplements (over-the-counter, generic). There is no prescription medication to cure lactose intolerance. Treatment focuses on diet changes and ensuring you get enough calcium and vitamin D from other sources.

When is surgery considered?

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Living with this condition

Living with lactose intolerance means being mindful of what you eat, but you can still enjoy a varied diet. Many people learn to read labels and plan meals to avoid discomfort.

Lifestyle tips

• Read food labels for hidden lactose in breads, cereals, salad dressings, and processed meats
• Keep a food diary to notice which foods cause symptoms
• Cook with lactose-free milk or plant-based alternatives
• Eat plenty of calcium-rich foods like leafy greens, broccoli, almonds, and fortified juices
• Talk to your doctor or dietitian about calcium and vitamin D supplements if needed

Diet and exercise

A healthy diet is still possible. Focus on fruits, vegetables, whole grains, lean proteins, and non-dairy sources of calcium. Exercise does not affect lactose intolerance directly, but regular activity supports overall digestion and health.

Mental health and emotional wellbeing

Adjusting to a new diet can be frustrating, especially at social events or when eating out. Some people feel anxious about accidentally eating lactose. It helps to plan ahead and carry lactase supplements. If you feel overwhelmed, talk to a healthcare professional.

Prevention

Lactose intolerance cannot be prevented in most cases because it is often genetic or age-related. You can manage it by watching your diet and keeping your gut healthy. Secondary lactose intolerance may be prevented by treating the underlying condition that damages the small intestine.

Vaccines

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Screening programmes

There is no routine screening test for the general population. People are tested only if they have symptoms.

Complications

If left untreated

• Osteoporosis (weak, brittle bones) due to poor absorption of calcium over time
• Vitamin D deficiency, which can affect bone health
• Malnutrition if you avoid all dairy without getting calcium and other nutrients from other foods
• Dehydration if diarrhea is severe and long-lasting

Long-term outlook

The outlook for lactose intolerance is very good. Most people can manage their symptoms with simple diet changes and avoid serious health problems. With the right support, you can lead a full and healthy life without discomfort.

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