Diabetes explained: type 1 versus type 2

What is diabetes and how insulin works

When we eat, food is broken down into glucose, a sugar that fuels the body. A hormone called insulin, made by the pancreas, acts like a key that lets glucose move from the blood into the body's cells to be used for energy. In diabetes, this system breaks down. Either the pancreas cannot make insulin, or the body stops responding to it properly, or both. The result is glucose building up in the blood instead of powering the cells. Over time, high blood glucose can damage blood vessels and nerves, which is why keeping levels in a healthy range matters so much. The two main types differ in exactly how the insulin system fails.

Type 1 diabetes

Type 1 diabetes is an autoimmune condition, meaning the body's own immune system mistakenly attacks and destroys the insulin-making cells in the pancreas. As a result, the body makes little or no insulin, so people with type 1 need insulin every day for life to survive. It is not caused by lifestyle or diet, and it cannot be prevented. Type 1 often starts in childhood or young adulthood, but it can appear at any age. Symptoms tend to come on quickly, over days or weeks: passing a lot of urine, being very thirsty, losing weight without trying, and feeling extremely tired. Because it can develop fast and become dangerous, these symptoms need urgent medical assessment.

Type 2 diabetes

Type 2 diabetes is far more common and develops differently. Here the body still makes insulin but does not respond to it properly — called insulin resistance — and over time the pancreas cannot keep up. It usually develops gradually in adults, though it is increasingly seen in younger people. Risk is higher with being overweight, being inactive, older age, family history, and in people of South Asian, African-Caribbean and Black African backgrounds. Symptoms are similar to type 1 but often milder and slower, so many people have it for years without knowing. It is frequently picked up on a routine blood test. Importantly, type 2 can often be improved, and sometimes put into remission, through changes to diet, weight and activity.

How each is treated

Treatment reflects the different causes. Type 1 always needs insulin, given by injection or an insulin pump, carefully balanced with food and activity, and supported by blood glucose monitoring — increasingly with wearable sensors that track levels continuously. Type 2 treatment starts with support for healthy eating, activity and weight, which can be powerful on its own. If needed, tablets and other medicines help the body use insulin better or lower glucose in other ways, and some people with type 2 eventually need insulin too. Both types involve regular NHS checks of the eyes, feet, kidneys and blood pressure to catch and prevent complications early. The aim in both is steady blood glucose and long-term health.

Living well and spotting problems

Whichever type, the everyday goals are similar: eat a balanced diet, stay active, attend regular reviews, and learn to recognise when blood sugar swings too high or too low. Low blood sugar (a hypo), more common with insulin, can cause shakiness, sweating, confusion and, if severe, collapse — and needs fast-acting sugar. Very high blood sugar, especially in type 1, can lead to a dangerous condition called diabetic ketoacidosis, with vomiting, tummy pain, deep breathing and drowsiness, which is a medical emergency. Structured education courses, diabetes nurses and GP teams all help people manage confidently. With good care, most people with diabetes live full, active lives while reducing their risk of long-term complications.