Get a Diagnosis
Your doctor may ask you to keep a diary of the foods you eat, to note when you have symptoms, and to stop eating an offending food to see if your symptoms go away. To make a diagnosis, some doctors simply look at your symptoms and whether avoiding dairy products for 2 weeks relieves them.
To confirm the diagnosis, your doctor may do other tests, such as:
Hydrogen breath test. Normally, people have very little hydrogen in their breath. If your body doesn't digest lactose, though, hydrogen builds in your intestines, and after a while it's in your breath. This test measures how much hydrogen is in your breath after you have a lactose-loaded drink several times in a few hours. If your levels are high 3 to 5 hours later, your body does not digest lactose well.
Lactose tolerance test. When your body breaks down lactose, it releases sugar into your blood. This tests how much sugar is in your blood. After you fast, a small sample of blood is taken. Then, you drink a liquid that is high in lactose. Two hours later, you give another blood sample. Because lactose causes blood sugar levels to rise, your blood sugar levels in this sample should be higher. If you're lactose intolerant, you'll have just a low rise in blood sugar and symptoms.
How to Manage Lactose Intolerance
You can't change how well your body digests lactose, but you can cut or even stop your symptoms.
Talk with your doctor or a registered dietitian who can help you plan a healthy diet that keeps you feeling good. Keep a food diary to help you learn how much (if any) dairy you can eat without having symptoms. Many people don't need to stop eating all dairy.
If you make small changes in what you eat, you may be able to prevent symptoms by helping your body digest dairy foods easier.
Don't eat dairy alone. It's easier for your body to digest lactose when you eat it with other foods. So try having small amounts of milk or dairy foods with meals.