A common guideline is about 1,000 FCC units of lactase for every 1–2 grams of lactose, though the right amount varies from person to person. Our lactose calculator estimates the lactose in your meal and suggests a starting dose. If you still notice symptoms, increase it gradually. EFSA's approved guidance is at least 4,500 FCC units with each lactose-containing meal.

FCC (Food Chemicals Codex) units measure how active a lactase enzyme is, meaning how much lactose it can break down. They are not a weight, so a tablet's milligrams tell you nothing about its strength. Compare FCC figures between products instead. A 9,000 FCC tablet, for example, is twice as strong as a 4,500 FCC one, whatever either tablet weighs.

FCC and ALU both measure lactase activity, but they are tested under different conditions, so the numbers can't be compared one-to-one. FCC is the standard used by most UK and EU lactase supplements, including Lea Gogo. If you're switching brands, check which unit each one uses before comparing strengths.

The number of tablets depends on how much lactose is in your meal and how sensitive you are. Lactose intolerance is very personal and everyone reacts differently to the same amount of lactose. It's often recommended to test and learn and see how much lactase gives you the right support for your favorite dairy dishes.

Lactose content varies widely between dairy foods:

• A 200ml glass of cow's milk contains roughly 9–10g.
• A pot of yoghurt contains around 4–6g.
• Aged hard cheeses like cheddar and parmesan contain almost none, typically under 0.1g per 100g.
• A slice of pizza is usually low to moderate, depending on the cheese and toppings.

The calculator adds these amounts up for a whole meal.

Lactose intolerance varies from person to person. Some people react heavily at the smalles lactose amount, whilst others are fine with most dishes and only start reacting after 2 cups of cappucino for example.

Lactase is a digestive enzyme that works on lactose in your gut. It is generally well tolerated, and taking slightly more than you need isn't considered harmful. Follow the dosage on your product label. If you have ongoing digestive symptoms, speak to a GP, because they may not be caused by lactose.

Take lactase with the first bite or sip of food that contains dairy, because the enzyme needs to be in your gut at the same time as the lactose. If a meal lasts longer than about 30–45 minutes, for example a long dinner or dessert later on, taking a second dose can help.