Carb counting for beginners

Why count carbs at all?

Carbohydrates (sugar, starch and fibre) are the part of food that turns into glucose most directly. Two meals with the same calories can do very different things to your blood sugar depending on how many carbs they hold.

If you take insulin with meals, your care team may have given you an insulin-to-carb ratio, and that only works if the carb number going in is close. If you don't take insulin, knowing your carbs still helps you spot which meals push you high, and keep meals more even through the day.

Step 1: Read the label the right way

Packaged food is the easy part, but there are two traps.

1. Use Total Carbohydrate, not Sugars. Sugar is only part of the carbs. Bread, rice and pasta are mostly starch and still raise blood sugar.
2. Check the serving size. The carbs on the label are for one serving. If the bag says 2.5 servings and you eat the whole bag, multiply by 2.5.

Some people subtract part or all of the fibre, because fibre isn't digested into glucose. Labels outside the US often list carbs with fibre already taken out. Ask your care team whether you should count fibre, and then do it the same way every time.

Step 2: Learn a handful of 15 g portions

Many diabetes educators use 15 g of carbs as one "carb choice" or "exchange". You don't need to memorise a whole table. Learn the foods you eat most. These are rough figures:

Exact numbers depend on the brand, the size and how it was cooked. Use the label when you have one.

Step 3: Get a feel for portion sizes

Most carb counting mistakes are portion mistakes, not maths mistakes. A restaurant plate of pasta can be two or three cups, not one.

• Weigh for a week. Put your usual bowl of rice or cereal on a kitchen scale a few times. You'll be surprised, then you'll be better at guessing.
• Use your own dishes. Once you know your usual bowl holds about 1 cup of rice, you don't need to weigh it again.
• Watch the hidden carbs. Sauces, breading, dressings, smoothies and juice add up quickly.

Step 4: Add it up for the whole plate

Count each food on its own, then add them. For a plate of grilled chicken, a cup of cooked rice and a side of green salad:

• Chicken: about 0 g
• 1 cup cooked white rice: about 45 g
• Salad with a little dressing: about 5 g
• Total: about 50 g

Protein and fat don't add many carbs, but a high-fat meal like pizza can make your blood sugar rise later and for longer. That's worth knowing when you look at your readings afterwards.

Step 5: Check your guess against your blood sugar

This is the step most people skip. Write down your carbs, then look at your reading about 2 hours after you started eating. If the same meal keeps sending you higher than you expected, your carb count for it is probably low. Our guide to blood sugar 2 hours after eating explains what to look for.

Common beginner mistakes

• Counting sugar instead of total carbs.
• Ignoring drinks. A glass of orange juice can have 25 g or more.
• Forgetting the second helping. Count what you actually ate, not what you planned.
• Trusting "sugar-free". Sugar-free biscuits still have flour, and flour is carbs.
• Expecting perfection. Even dietitians are off by a few grams. Consistent and close is the goal.

Where an app can help

Counting gets easier with practice, but some meals, like a mixed plate at a restaurant, are still hard to guess. In T1dApp you can take a photo of your plate and get carbs for each food, plus the meal's calories, protein and fat. The numbers are estimates shown as a range, and you can edit them before saving. Two hours later the app asks for your reading, so you learn how your guesses line up with what really happened.

Sources

• American Diabetes Association. Nutrition Therapy for Adults With Diabetes or Prediabetes: A Consensus Report (2019)
• American Diabetes Association. Standards of Care in Diabetes

This article is general information, not medical advice. Your targets, doses and diet should be set with your doctor or diabetes care team.