Lactose Intolerance: How to Get Diagnosed and Eat Without Pain

Most people think if you can't drink milk without bloating, you have lactose intolerance. But that’s not always true. Some people can drink a glass of milk just fine. Others get sick from a spoonful of yogurt. The problem isn’t always the same, and neither is the solution. Lactose intolerance isn’t an allergy. It’s not even always a disease. It’s your body’s natural inability to break down lactose - the sugar in milk - because it doesn’t make enough of the enzyme lactase. And if you’ve been told you have it, you might be cutting out dairy unnecessarily. Or worse, you might be missing out on calcium and vitamin D because no one told you how to replace them.

How Do You Know It’s Lactose Intolerance?

Symptoms like bloating, gas, cramps, and diarrhea usually show up 30 minutes to two hours after eating dairy. But here’s the catch: not everyone with low lactase levels feels symptoms. Studies show that up to 30% of people who test positive for lactose malabsorption don’t have any discomfort at all. That’s why diagnosis isn’t just about a lab test. It’s about matching your symptoms to your diet.

The first step most doctors take is a simple elimination diet. Cut out all dairy for two to four weeks. That means no milk, cheese, yogurt, ice cream, butter, or even hidden lactose in bread, salad dressings, and protein bars. If your symptoms disappear, that’s a strong clue. Then, you slowly add dairy back in - one food at a time - to see what you can handle. This isn’t fancy, but it’s the most real-world test you can do. It tells you what your body actually reacts to, not just what a machine says.

The Hydrogen Breath Test: The Gold Standard

If your symptoms are confusing or your doctor wants proof, they’ll likely send you for a hydrogen breath test. This is the most reliable test available. You drink a liquid with 25 to 50 grams of lactose - roughly the amount in a large glass of milk. Then, you breathe into a tube every 30 minutes for two to three hours. The machine measures how much hydrogen is in your breath.

Here’s why it works: when your body can’t digest lactose, bacteria in your colon ferment it. That fermentation releases hydrogen gas. Some of it gets absorbed into your blood and comes out through your lungs. If your breath hydrogen rises more than 20 parts per million above your starting level, you’re likely malabsorbing lactose. The test is 90% accurate at detecting this. But it’s not perfect.

It can give false positives if you have small intestinal bacterial overgrowth (SIBO), which affects about 15% of people. You also have to fast for 12 hours before the test and avoid antibiotics for four weeks. And if you’re on the NHS in the UK, you might wait months for an appointment. One Reddit user waited eight months before getting tested - and was misdiagnosed with IBS in the meantime.

What About Blood Tests and Genetic Tests?

The lactose tolerance blood test checks your blood sugar after you drink lactose. If your glucose doesn’t rise by at least 20 mg/dL, your body isn’t breaking down the sugar. But this test has a 20% error rate because stomach emptying varies from person to person. It’s also invasive - you need multiple blood draws. Most doctors don’t use it anymore.

Genetic tests look for a specific mutation (C/T-13910) linked to lactase non-persistence. It’s 95% accurate for predicting whether you’ll have lifelong lactose intolerance. But it only tells you about primary lactase deficiency - the kind you’re born with. It won’t catch lactose intolerance caused by illness, surgery, or gut damage. And it won’t tell you how much lactose you can actually tolerate. So while it’s useful for research, it’s not the best tool for daily life.

How Much Lactose Can You Really Handle?

Here’s the good news: you don’t have to give up dairy completely. Most adults can handle up to 12 grams of lactose in one sitting - that’s about a cup of milk. And if you eat it with food, you can often handle up to 18 grams. Hard cheeses like cheddar or parmesan have almost no lactose. Yogurt with live cultures breaks down much of the sugar naturally. Many people find they can eat these without symptoms.

Studies show that 73% of people diagnosed with lactose intolerance can tolerate small amounts of cheese or yogurt. Yet most diets tell you to avoid everything. That’s why so many people feel confused. You’re not broken. You just need to find your personal limit.

What About Lactase Pills?

Lactase enzyme supplements - like Lactaid® - can help. Take 3,000 to 9,000 FCC units right before eating dairy. In clinical trials, they reduce symptoms by 70 to 90%. They work best when taken with the first bite of food. But they’re not magic. If you eat a whole pizza with multiple cheeses, you might still feel bloated. They’re a tool, not a license to binge on ice cream.

Replacing Calcium and Vitamin D

One of the biggest risks of cutting out dairy is nutrient deficiency. About 70% of teens get most of their daily calcium from milk and cheese. If you stop drinking milk, you need to replace it - fast.

Fortified plant milks (almond, oat, soy) typically contain 300 to 500 mg of calcium per 8-ounce serving. That’s close to cow’s milk. Calcium-set tofu, kale, bok choy, broccoli, and canned salmon with bones are also good sources. Aim for 1,000 to 1,200 mg of calcium a day. For vitamin D, get sunlight, eat fatty fish, or take a supplement. The NHS recommends 10 micrograms daily for adults.

Don’t assume all “non-dairy” products are safe. A 2022 FDA audit found 20% of products labeled “non-dairy” still contain trace lactose. Always check the ingredients for milk solids, whey, curds, or milk powder.

The New Rules: Personalized Tolerance

Europe’s food safety agency updated its guidelines in 2023 to reflect what science now knows: lactose tolerance varies by age. Adults can handle 12 grams. Kids 4 to 8 can handle 8 grams. Kids under 4? Only 4 grams. That’s why toddlers often react to yogurt - not because they’re allergic, but because their systems are still developing.

Doctors are starting to move away from one-size-fits-all advice. The American Gastroenterological Association now says diagnosis should be based on symptoms, not just test results. If you feel fine after eating cheese, you don’t need to avoid it - even if your breath test was positive.

What’s Changing in 2025?

New tools are making life easier. The LactoQuik® breath test, approved in 2022, cuts testing time from three hours to 45 minutes. It’s already in use in many U.S. clinics and is coming to the UK. Probiotics like Pendulum’s LactoSpore® are showing promise in early trials - they help your gut digest lactose better, reducing symptoms without pills.

Apps like MyLactaseTracker® are helping people log what they eat and how they feel. Over 60% of gastroenterology practices now use them. They turn guesswork into data. You can see patterns: “I’m fine with yogurt on weekdays but bloated after weekend ice cream.” That kind of insight is powerful.

Don’t Let Misinformation Starve You

Overdiagnosis is real. A 2023 JAMA study found 35% of people diagnosed with lactose intolerance based on breath tests could eat normal dairy portions without symptoms. That means thousands are avoiding dairy unnecessarily - and risking bone health, muscle function, and overall nutrition.

And if you’re cutting out dairy because you think it’s “inflammatory” or “toxic,” you’re being misled. There’s no evidence that lactose intolerance is linked to inflammation unless you’re consuming way more than your body can handle. Dairy isn’t the enemy. Lack of knowledge is.

What you need is clarity. Not fear. A test. A plan. And permission to eat what works for you - not what a brochure says you should avoid.