What Is Insulin Resistance?

Insulin resistance is one of the most important ideas in metabolic health, yet it is rarely explained clearly. In simple terms, it is the point at which your body stops responding as well as it should to insulin — the hormone that lets your cells take sugar out of the bloodstream for energy. It often develops silently over years and is an early step on the road towards type 2 diabetes, which is why understanding and detecting it matters.

How insulin normally works

After you eat, carbohydrates are broken down into glucose, which enters the blood. Your pancreas releases insulin, which acts like a key, unlocking cells so they can absorb that glucose. When everything works smoothly, blood sugar rises briefly after a meal and then settles back down. Insulin resistance means the "lock" has become stiff: cells respond sluggishly, so the pancreas has to produce more and more insulin to get the same result.

Why it matters

For a while, the pancreas keeps up by making extra insulin, and blood sugar stays normal. But this comes at a cost. High circulating insulin encourages fat storage, particularly around the middle, and is linked to raised blood pressure and unfavourable cholesterol patterns. Over time, if the pancreas can no longer keep pace, blood sugar starts to rise — first into the pre-diabetes range, then potentially into type 2 diabetes.

What increases the risk

Several factors make insulin resistance more likely, and many overlap:

• Excess weight, especially around the abdomen — one of the strongest drivers.
• Physical inactivity — muscles that move regularly use glucose more efficiently.
• Polycystic ovary syndrome (PCOS) — closely tied to insulin resistance in women.
• Non-alcoholic fatty liver disease — often goes hand in hand with it.
• Family history and certain ethnic backgrounds — which raise baseline risk.

How it is assessed

There is no single perfect test for insulin resistance in everyday practice, but blood tests give a strong picture. HbA1c shows whether your average blood sugar is creeping up, which is one of the clearest downstream signs. A fasting insulin level, where used, can add information about how hard the pancreas is working. Your clinician interprets these together with your weight, waist, blood pressure and cholesterol to judge your overall metabolic risk.

The good news: it can improve

Insulin resistance is often reversible, particularly in its earlier stages. Losing even a modest amount of weight if you carry extra, building regular physical activity into your week, improving sleep, and cutting back on sugary drinks and refined carbohydrates can all make cells more responsive to insulin again. Because progress can be tracked with something as simple as a repeat HbA1c, it is easy to see whether your efforts are paying off — ideally with a doctor helping you interpret the trend and set realistic goals.

Written by Dr Ibrar Ahmed — MBChB MRCP MRCGP PhD PG Dip (Cardiology)
Specialist interest: Cardiovascular Medicine · OneMedicine, CQC-registered clinic