Lactose intolerance living in teenagers

Overview

Lactose intolerance means your body has trouble digesting lactose, a natural sugar found in milk and dairy products. It happens when your small intestine doesn't make enough lactase, the enzyme that breaks down lactose. This can cause uncomfortable symptoms after eating dairy, but it's not dangerous.

Yes, it is quite common. Around 65–70% of the world's population has some degree of lactose intolerance. It is especially common in people of Asian, African, and Hispanic descent.

It can affect anyone, but it often starts in adolescence or early adulthood. Teenagers may notice symptoms for the first time when they get older.

Symptoms

Common symptoms

• Bloating and gas after eating dairy
• Stomach cramps or pain
• Diarrhoea or loose stools
• Nausea, sometimes with vomiting

Symptoms in children

• Irritability after feeding
• Fussiness or crying
• Loose, watery stools
• Refusing to eat or drink

Symptoms in older adults

• Bloating and gas (similar to younger adults)
• Diarrhoea may be more severe and lead to dehydration

Causes

Main causes

• Your body stops making enough lactase enzyme as you get older (primary lactose intolerance)
• Damage to the small intestine from illness, infection, or conditions like coeliac disease (secondary lactose intolerance)
• A rare condition where a baby is born without lactase (congenital lactase deficiency)

Risk factors

• Family history of lactose intolerance
• Being of Asian, African, or Hispanic descent
• Intestinal infections or diseases like Crohn's disease
• Premature birth (babies born early may have less lactase)

When to see a doctor

See a doctor urgently if:

• Severe pain that does not go away
• Blood in your stool or vomit
• Signs of dehydration (see emergency section)

Book a routine appointment if:

• You regularly feel bloated or have diarrhoea after eating dairy
• You think dairy is affecting your school or social life
• You want to confirm the cause of your symptoms

Diagnosis

Doctors diagnose lactose intolerance by talking about your symptoms and medical history. They may ask you to keep a food diary and try a dairy-free diet for a while. If needed, they can do simple tests to confirm.

Tests that may be done

• Hydrogen breath test: You drink a lactose solution and then breathe into a device. Higher hydrogen levels mean you are not digesting lactose fully.
• Lactose tolerance blood test: Your blood sugar is checked after you drink lactose. If it does not rise much, lactose is not being broken down.
• Stool acidity test (more common for young children): Stool is tested for acid that forms when undigested lactose ferments.

What to expect at your appointment

The tests are simple and non-invasive. You may be asked to avoid dairy for a short time before. The doctor will explain the results and work with you on a plan.

Treatment

There is no cure for lactose intolerance, but most people can manage it with diet changes. The goal is to avoid or limit lactose while still getting all the nutrients you need.

Self-care at home

• Try lactose-free or dairy-free milk, yoghurt, and cheese.
• Eat smaller amounts of dairy at one time (some people can handle a little).
• Pair dairy with other foods to slow digestion (e.g., cheese on a cracker).
• Take lactase enzyme supplements (over the counter) with dairy products if you want to eat them.
• Check food labels for hidden lactose (whey, milk solids, etc.).

Medical treatments

Doctors may recommend lactase enzyme supplements that you can buy without a prescription. These help digest lactose when taken with dairy. Some people find probiotics helpful, but talk to your doctor first. No prescription medications are specifically for lactose intolerance unless it is secondary to another condition.

When is surgery considered?

Surgery is never needed for lactose intolerance.

Living with this condition

Living with lactose intolerance as a teenager can feel tricky, especially at parties, school lunches, or eating out. But with a little planning, you can still enjoy meals with friends. Many shops sell lactose-free versions of your favourite dairy foods. You can also try plant-based milks like soya, oat, or almond.

Lifestyle tips

• Tell your friends and family about your needs so they can support you.
• Plan ahead when eating out: check menus online or ask for dairy-free options.
• Carry a small supply of lactase pills in your bag if you want to eat dairy occasionally.
• Explore new recipes that are dairy-free—there are lots of tasty alternatives.

Diet and exercise

Cutting out dairy means you need to get calcium and vitamin D from other sources. Good options include leafy green vegetables, fortified plant milks, almonds, and tinned fish with bones (like sardines). Exercise is fine—just be mindful if you have symptoms after a meal. Staying active is important for your overall health.

Mental health and emotional wellbeing

Feeling different from your friends because of food restrictions can be hard. You might feel self-conscious or left out. It’s normal to feel frustrated sometimes. Talk to a trusted adult, like a parent or school counsellor, about your feelings. You are not alone.

Prevention

Primary lactose intolerance (the most common type) cannot be prevented because it is genetic. However, you can prevent symptoms by managing how much lactose you eat. Secondary lactose intolerance from infections can sometimes be avoided by treating the underlying condition early.

Screening programmes

There is no routine screening for lactose intolerance. If you have symptoms, see your doctor for a proper evaluation.

Complications

If left untreated

• Ongoing discomfort like bloating and diarrhoea that can interfere with school and social life
• Nutritional deficiencies if you avoid dairy without replacing calcium and vitamin D (risk of weak bones)
• Dehydration from severe diarrhoea (rare)

Long-term outlook

The outlook is very good. Most teenagers can find a way to manage their symptoms without missing out on too much. You can enjoy a full, healthy diet with simple swaps. Your body may even change over time—some people become less sensitive as they get older.

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