Type 1 diabetes

What happens in type 1

The immune system attacks and destroys the beta cells of the pancreas, which are the only cells in the body that make insulin. The loss is permanent and eventually near-total. Without insulin, glucose cannot enter cells; the body burns fat instead and produces ketones, which are acidic. That is the process behind diabetic ketoacidosis.

Because the deficiency is absolute rather than relative, insulin is not one option among several. It is replacement of something the body no longer produces, and it is needed from diagnosis, for life.

It is not only a childhood condition

This is the most consequential misunderstanding about type 1. It can begin at any age, and a large share of new cases — by many estimates around half — start in adulthood. Slowly progressive forms in adults are frequently labelled type 2 at first, because the patient is an adult and the onset is gradual.

The consequence of that error is real. Someone with type 1 treated as type 2 will respond poorly to tablets, be told they are not trying hard enough, and remain at risk of ketoacidosis. If glucose control deteriorates quickly on oral medicines, if weight is falling, or if there is a personal or family history of other autoimmune disease such as thyroid or coeliac disease, the diagnosis deserves to be questioned. Antibody testing and a C-peptide level can usually settle it.

Day-to-day management

Insulin is given as a background dose that covers the body's baseline needs, plus doses at meals matched to the carbohydrate eaten and to the glucose reading at the time. Getting the meal doses right depends on being able to estimate carbohydrate — which is a learnable skill, and one of the reasons the carbohydrate counter on this site is built around Pakistani portions rather than Western ones.

Monitoring is not optional in type 1. Whether by finger-prick testing several times a day or by continuous glucose monitoring, dosing without readings is guesswork. Hypoglycaemia is the constant counterweight to tight control, and knowing how to recognise and treat it — and making sure the people around you also know — is as important as the insulin itself.

Sick days

Illness raises glucose even when you are eating less, and it is the commonest route into ketoacidosis. The rule that surprises people is that insulin is never stopped during illness, even if you cannot eat. Doses may need to go up, glucose and ketones need checking more often, and fluids matter. Everyone with type 1 should have been given clear sick-day rules before they need them.