Insulin-to-Carb Ratios, Simply

Once you are counting carbohydrate, you need something to convert that count into a dose. That is your insulin-to-carbohydrate ratio.

It expresses how many grams of carbohydrate one unit of your mealtime insulin covers. If your ratio is one unit to ten grams, and your lunch contains fifty grams of carbohydrate, your meal dose is five units.

Two things surprise people. First, the ratio is personal — it is worked out for you and can be quite different from someone else's. Second, it often differs by time of day. Many people are more resistant to insulin in the morning and need proportionally more for breakfast than for the same food at dinner.

There is usually a second number too, a correction factor, which says how far one unit will bring down a high reading. Your mealtime dose is then the meal calculation plus a correction if you are already high.

These numbers are starting estimates that get refined from your readings. If a particular meal reliably leaves you high two hours later despite correct counting, the ratio for that meal probably needs changing.

That refinement is a conversation with your team, based on a week of paired readings rather than one bad afternoon.