The most common signs of insulin resistance include excess belly fat (especially a waist over 35" for women or 40" for men), persistent fatigue after carb-heavy meals, intense sugar cravings — particularly in the afternoon — difficulty losing weight despite diet and exercise, dark velvety patches of skin on the neck or armpits (acanthosis nigricans), and small skin tags. In women, irregular periods and symptoms consistent with PCOS are also strongly associated. An insulin resistance symptoms checklist like this quiz can be a useful starting point, but a blood test is the only way to confirm. High triglycerides combined with low HDL cholesterol is one of the clearest metabolic markers seen on a standard lipid panel.

The gold-standard clinical test is the HOMA-IR (Homeostatic Model Assessment of Insulin Resistance) test. It uses two fasting blood values — fasting glucose and fasting insulin — and applies a simple formula: (fasting insulin × fasting glucose) ÷ 405 (using mg/dL). A HOMA-IR score below 1.0 is considered optimal; above 1.9 suggests early insulin resistance; above 2.9 is significant. Many GPs will run fasting glucose and HbA1c routinely, but you may need to specifically request a fasting insulin level to calculate HOMA-IR. As for how to test for insulin resistance at home, there is currently no reliable home test — continuous glucose monitors (CGMs) can offer helpful insights into blood sugar patterns but cannot directly measure insulin. The most practical step is to ask your doctor for a fasting insulin and fasting glucose test together.

What causes insulin resistance is multi-factorial. The most significant contributors are excess body fat (especially visceral fat around the organs), a diet high in refined carbohydrates and ultra-processed foods, physical inactivity, chronic stress (which elevates cortisol), poor sleep, and genetics — particularly if a parent or sibling has type 2 diabetes. Hormonal conditions like PCOS also drive insulin resistance directly. The encouraging news is that insulin resistance is highly reversible for most people. Studies consistently show that even a 5–10% reduction in body weight, combined with regular physical activity and a lower-glycaemic diet, can dramatically improve insulin sensitivity — sometimes normalising it entirely within weeks to months.

The best insulin resistance diet focuses on reducing blood sugar spikes and supporting fat loss. Evidence-backed principles include: replacing refined carbohydrates (white bread, sugary drinks, pastries) with fibre-rich whole foods (vegetables, legumes, whole grains); prioritising protein at every meal to slow glucose absorption and support satiety; incorporating healthy fats from olive oil, avocado, and nuts; reducing ultra-processed foods and added sugars; and eating meals earlier in the day where possible (time-restricted eating has shown promising results). The Mediterranean diet and lower-carbohydrate diets both have strong evidence for improving insulin sensitivity. Always make dietary changes in consultation with a healthcare professional, particularly if you take medication.

No — but they exist on the same spectrum. Insulin resistance is the underlying mechanism: your cells stop responding properly to insulin, so the pancreas compensates by producing more. Prediabetes is diagnosed when blood glucose levels are elevated but not yet in the diabetic range (typically fasting glucose 100–125 mg/dL or HbA1c 5.7–6.4%). Type 2 diabetes occurs when the pancreas can no longer keep up with the demand and blood sugar rises into the diabetic range. You can have significant insulin resistance for years before blood sugar starts rising — which is why fasting insulin is a more sensitive early marker than glucose alone. Catching and addressing insulin resistance early, before it progresses to prediabetes, is the optimal window for reversal.