'Blood sugar' comes up constantly in discussions of diet and diabetes, but what is it, really? Here's the plain-language version.
Glucose: your body's fuel
Blood sugar, or blood glucose, is the amount of the sugar glucose circulating in your bloodstream. Glucose is the body's primary fuel — your brain alone runs almost entirely on it. When you eat carbohydrates, they break down into glucose, which enters the blood and is delivered to cells for energy.
The role of insulin
The hormone insulin, made by the pancreas, is the key that lets glucose move from the blood into cells. After a meal, blood sugar rises, the pancreas releases insulin, and cells take up the glucose, bringing blood sugar back down. Another hormone, glucagon, raises blood sugar when it drops too low. This push-pull keeps levels in a healthy range.
Spikes and why they matter
Different foods raise blood sugar at different speeds — the idea behind the glycemic index. A sugary drink causes a fast, steep spike because it's pure, fiber-free sugar. A bowl of oatmeal releases glucose slowly. Occasional spikes are normal, but frequent large ones make the pancreas work hard and, over years, can contribute to insulin resistance.
When regulation breaks down
In prediabetes and type 2 diabetes, the insulin system stops keeping up — either the body resists insulin or doesn't make enough — and blood sugar stays elevated. Chronic high blood sugar damages the body over time, which is why managing it is central to diabetes care.
Keeping it steady
Fiber, protein, and fat all slow glucose absorption and blunt spikes, which is why whole foods affect blood sugar more gently than refined sugar and juice. Pairing carbs with protein or fiber, and favoring drinks without added sugar, helps keep levels stable.