Signs of Insulin Resistance: Symptoms and Risks

Signs of insulin resistance can be subtle and easy to overlook, yet identifying them early is key to preventing serious long-term conditions such as type 2 diabetes and cardiovascular disease. Insulin resistance occurs when the body's cells become less responsive to insulin, prompting the pancreas to produce more of the hormone to compensate. Common indicators include fatigue, central weight gain, acanthosis nigricans, and irregular periods. Because many people have no obvious symptoms for years, understanding the risk factors, diagnostic pathways, and associated health conditions is essential for timely action and effective management.

What are the most common signs of insulin resistance?

The most common signs include acanthosis nigricans, central weight gain, persistent fatigue, increased hunger after eating, and irregular periods. Insulin resistance can be silent for years, so blood tests are needed for confirmation.

The most common signs of insulin resistance include persistent fatigue, difficulty losing weight, increased hunger shortly after eating, and a darkening of the skin in body folds known as acanthosis nigricans. Insulin resistance occurs when the body's cells respond less effectively to insulin, the hormone produced by the pancreas that allows glucose to enter cells for energy. As a result, the pancreas compensates by producing more insulin, and blood glucose levels can gradually rise over time.

Physical signs that may prompt further investigation include:

• Acanthosis nigricans: dark, velvety patches of skin around the neck, armpits or groin

• Central weight gain: excess fat carried around the abdomen rather than the hips or thighs

• Persistent fatigue and brain fog: particularly after carbohydrate-rich meals; these symptoms are non-specific and can have many causes, so objective blood tests are needed alongside any symptom assessment

• Increased thirst and more frequent urination: which may indicate rising blood glucose levels

• Irregular menstrual cycles: in women, often associated with polycystic ovary syndrome (PCOS)

It is important to note that insulin resistance can be present for years without causing obvious symptoms, which is why it is sometimes referred to as a silent condition. Many people are only identified during routine blood tests or when a related condition such as type 2 diabetes or PCOS is diagnosed.

If you develop marked thirst, very frequent urination, unexplained weight loss, or feel drowsy or unwell, contact your GP promptly or call NHS 111, as these can be signs of significantly raised blood glucose that need timely assessment. If you notice several of the signs listed above together, particularly alongside unexplained weight gain or fatigue, it is worth discussing them with your GP, who can arrange appropriate investigations.

What causes insulin resistance and who is most at risk in the UK?

Excess visceral fat is the strongest modifiable cause, with additional risk from physical inactivity, refined carbohydrate intake, and family history. People of South Asian or Black African heritage face higher risk at lower BMI thresholds.

Insulin resistance develops when a combination of genetic, lifestyle and metabolic factors reduces the sensitivity of cells, particularly in muscle, fat and liver tissue, to the effects of insulin. Excess body fat, especially visceral fat stored around the abdominal organs, is one of the strongest modifiable drivers. Visceral fat releases inflammatory signals and free fatty acids that interfere with insulin signalling pathways, making it harder for glucose to be taken up by cells.

Several factors increase the risk of developing insulin resistance in the UK population:

• Overweight and obesity: In UK practice, waist circumference thresholds vary by ethnicity. For people of European origin, risk increases above 94 cm in men and 80 cm in women. For people of South Asian, Chinese or Japanese origin, lower thresholds apply (approximately 90 cm in men and 80 cm in women), reflecting greater metabolic risk at smaller waist sizes.^[5] The NHS also uses ethnicity-adjusted BMI thresholds: for South Asian, Chinese, and other high-risk ethnic groups, overweight is defined as a BMI of 23 kg/m2 or above, and obesity as 27.5 kg/m2 or above, compared with 25 and 30 kg/m2 respectively for white European populations.

• Physical inactivity: sedentary behaviour reduces the muscles' ability to use glucose efficiently

• Diet high in refined carbohydrates and ultra-processed foods: associated with repeated spikes in blood glucose and insulin; UK public health guidance recommends reducing intake of foods high in free sugars and refined starches

• Family history: a first-degree relative with type 2 diabetes significantly raises personal risk

• Ethnicity: people of South Asian, Black African or Black Caribbean heritage develop insulin resistance at lower BMI thresholds and at younger ages, a pattern recognised in NHS guidance

• Sleep disorders: particularly obstructive sleep apnoea, which disrupts hormonal regulation and is associated with impaired glucose metabolism^[8][9]

• Certain medicines: including long-term corticosteroids and some antipsychotics, which can raise blood glucose and contribute to insulin resistance.^[6][7] If you think a medicine you are taking may be affecting your blood glucose, speak to your GP or pharmacist. Suspected side effects of any medicine can also be reported to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk.

• Hormonal conditions: such as PCOS, Cushing's syndrome, and hypothyroidism; the link with hypothyroidism is variable and tends to improve with treatment of the underlying thyroid condition

Age is also a contributing factor, as insulin sensitivity tends to decline gradually from middle age onwards. However, insulin resistance is increasingly seen in younger adults and adolescents, reflecting rising rates of obesity and physical inactivity across the UK. Understanding personal risk factors is the first step towards making targeted lifestyle changes.

How is insulin resistance diagnosed by a GP or specialist?

GPs use fasting plasma glucose and HbA1c to identify non-diabetic hyperglycaemia, the most common indirect marker. An HbA1c of 42 to 47 mmol/mol indicates prediabetes and may prompt referral to the NHS Diabetes Prevention Programme.

Insulin resistance is typically identified through a combination of clinical assessment and blood tests rather than a single definitive diagnostic test. In UK primary care, a GP will usually begin by reviewing symptoms, measuring waist circumference and calculating BMI, then requesting fasting blood tests to assess glucose metabolism and related markers.

Key investigations a GP may arrange include:

• Fasting plasma glucose: the WHO defines impaired fasting glycaemia as 6.1 to 6.9 mmol/l, which is closely associated with insulin resistance. The NHS Diabetes Prevention Programme (NHS DPP) in England uses a broader referral range of 5.5 to 6.9 mmol/l for non-diabetic hyperglycaemia (NDH), so a result in this lower range may still prompt referral even if it does not meet the WHO impaired fasting glycaemia threshold.

• HbA1c (glycated haemoglobin): an HbA1c of 42 to 47 mmol/mol indicates non-diabetic hyperglycaemia (sometimes called prediabetes), as defined in NICE guideline NG238 on type 2 diabetes prevention.^[12][13] This is the threshold used to identify people eligible for the NHS DPP.

• Oral glucose tolerance test (OGTT): not used routinely in primary care, but may be considered in selected situations, such as when fasting glucose and HbA1c give discordant results, in the assessment of PCOS, or when assessing risk in pregnancy-related contexts.

• Fasting lipid profile: insulin resistance commonly produces a pattern of raised triglycerides and low HDL cholesterol

• Liver function tests: non-alcoholic fatty liver disease is a frequent companion of insulin resistance

• HOMA-IR (Homeostatic Model Assessment of Insulin Resistance): calculated from fasting insulin and glucose levels, this is used in research and specialist settings but is not routinely available in NHS primary care

A formal diagnosis of insulin resistance as a standalone condition is not always made in clinical practice. Instead, GPs often identify it indirectly through the presence of non-diabetic hyperglycaemia (NDH), metabolic syndrome or PCOS. NICE guideline NG238 recommends that people with NDH are offered referral to the NHS Diabetes Prevention Programme, which provides structured lifestyle support and is available in England; equivalent programmes exist in Scotland, Wales and Northern Ireland through their respective health services.^[12][13]

Bolt Pharmacy is a GPhC-registered online pharmacy (Great Britain) offering online weight-management consultations, with prescriber review and pharmacist support, which may be relevant for people seeking additional guidance alongside NHS care. If you are concerned about your results, ask your GP to explain what they mean for your individual risk.

What health conditions are linked to untreated insulin resistance?

Untreated insulin resistance significantly raises the risk of type 2 diabetes, cardiovascular disease, NAFLD, and PCOS. Early lifestyle intervention can meaningfully reverse insulin resistance and reduce progression risk.

Untreated insulin resistance significantly raises the risk of developing several serious long-term health conditions, most notably type 2 diabetes, cardiovascular disease and non-alcoholic fatty liver disease (NAFLD, also increasingly referred to as metabolic dysfunction-associated steatotic liver disease or MASLD).^[18] When the pancreas can no longer compensate for reduced cellular sensitivity by producing extra insulin, blood glucose rises into the diabetic range, at which point the damage to blood vessels and nerves can begin.

Conditions strongly associated with persistent insulin resistance include:

• Type 2 diabetes: the most direct consequence; Diabetes UK estimates that more than 4 million people are living with type 2 diabetes in the UK, with millions more at risk^[14]

• Cardiovascular disease: insulin resistance promotes hypertension, dyslipidaemia and endothelial dysfunction, all of which increase the risk of heart attack and stroke

• Non-alcoholic fatty liver disease (NAFLD/MASLD): excess insulin drives fat accumulation in liver cells, which can progress to non-alcoholic steatohepatitis (NASH) and, in some cases, cirrhosis

• Polycystic ovary syndrome (PCOS): insulin resistance is a central feature of PCOS and contributes to hormonal imbalance, irregular periods and fertility difficulties

• Metabolic syndrome: a cluster of conditions including central obesity, raised blood pressure, high triglycerides and low HDL cholesterol that together substantially increase cardiovascular risk

• Certain cancers: observational evidence suggests associations between chronic hyperinsulinaemia and cancers of the colon, breast and endometrium, though causality is not fully established and further research is ongoing^[15][16]

The encouraging finding from large UK and international studies, including evidence underpinning NICE guideline NG238, is that insulin resistance is largely reversible in its earlier stages. Sustained weight loss of 5 to 10 per cent of body weight, increased physical activity and dietary changes can meaningfully improve insulin sensitivity and reduce the risk of progression to type 2 diabetes.^[17] If you are concerned about any of the conditions listed above, contact your GP for a review rather than waiting for symptoms to worsen.

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