The glycaemic index (GI) is a 0 to 100 scale that ranks carbohydrate foods by how fast they raise blood glucose.

What the glycaemic index is

The glycaemic index is a way of ranking carbohydrate foods by how fast they raise blood glucose after eating. High-GI foods such as white bread and sugary drinks raise blood sugar quickly, while low-GI foods such as oats and most legumes release glucose more slowly and gradually. The scale only looks at the blood sugar effect, not the calories or the overall nutritional value of a food. See the PCOS diet page for a broader view of eating patterns.

How it relates to PCOS

Many women with PCOS have insulin resistance, meaning the body responds less well to insulin. As a result, sharp blood sugar spikes after meals can put extra strain on this system. Leaning towards more low-GI foods may help soften the blood sugar and insulin spikes that follow a meal, though it is only one part of an overall eating pattern. You can read more about the underlying cause on the insulin resistance page.

Why GI is not the whole story

GI is just one tool, not a single answer. Portion size, fibre, fat and protein content, and how a food is cooked all change its real effect on blood sugar. Foods are rarely eaten on their own, so pairing carbohydrates with protein or fibre can shift the response. A low GI also does not mean a food is automatically healthy, because some high-fat foods have a low GI but still need to be eaten in moderation.

How to use it in practice

Rather than focusing on a single number, it is more useful to think about the balance of a meal as a whole. For example, choosing whole grains over processed ones, or adding vegetables and protein to a meal, often helps more than simply chasing a low GI value. GI can act as a rough guide when making choices, but it does not replace personal advice, and each person responds a little differently to the same food. For an eating plan suited to your situation, medicines, and goals, it is best to talk with a doctor or dietitian who can assess your individual needs.

This glossary is education, not diagnosis. For your own situation, ask a doctor or pharmacist.