When most people think about insulin resistance, they think about diabetes. They imagine high blood sugar readings, a GP delivering a warning, and a prescription for lifestyle changes. But here's what doesn't get talked about nearly enough: insulin resistance can be quietly wreaking havoc in your body for years sometimes decades while your fasting glucose remains perfectly normal.
Normal blood sugar does not mean normal insulin. And that distinction matters enormously.
What Is Insulin Resistance?
Insulin is a hormone produced by the pancreas. Its primary job is to act as a key, unlocking your cells so that glucose from the bloodstream can enter and be used for energy. When cells become resistant to insulin's signal, the pancreas compensates by producing more insulin to get the same job done.
In the early stages of insulin resistance, this compensation works. Blood glucose stays in the normal range because the pancreas is simply working harder. Standard fasting glucose tests and even HbA1c measurements can look completely unremarkable. From a conventional screening standpoint, nothing appears wrong.
What's happening beneath the surface, however, is a different story. Chronically elevated insulin, a state called hyperinsulinaemia, drives inflammation, disrupts hormone signalling, promotes fat storage, and interferes with virtually every system in the body. The glucose reading is normal, but the metabolic environment is already under strain.
By the time blood sugar actually rises, insulin resistance has typically been present for years.
In the early stages of insulin resistance, this compensation works. Blood glucose stays in the normal range because the pancreas is simply working harder. Standard fasting glucose tests and even HbA1c measurements can look completely unremarkable. From a conventional screening standpoint, nothing appears wrong.
What's happening beneath the surface, however, is a different story. Chronically elevated insulin, a state called hyperinsulinaemia, drives inflammation, disrupts hormone signalling, promotes fat storage, and interferes with virtually every system in the body. The glucose reading is normal, but the metabolic environment is already under strain.
By the time blood sugar actually rises, insulin resistance has typically been present for years.
The Signs Your Body May Be Insulin Resistant
Fatigue After Eating
One of the most telling early signs is a significant energy crash after meals particularly meals containing carbohydrates. When cells aren't responding efficiently to insulin, glucose isn't being taken up and used for energy as it should be. The result is a post-meal slump that feels disproportionate to what you ate: drowsiness, brain fog, or a strong urge to lie down roughly 30-90 minutes after eating.
This is often dismissed as normal tiredness or written off as a sign of eating "too much." It isn't. Metabolically healthy individuals generally feel sustained energy after meals, not depletion.
One of the most telling early signs is a significant energy crash after meals particularly meals containing carbohydrates. When cells aren't responding efficiently to insulin, glucose isn't being taken up and used for energy as it should be. The result is a post-meal slump that feels disproportionate to what you ate: drowsiness, brain fog, or a strong urge to lie down roughly 30-90 minutes after eating.
This is often dismissed as normal tiredness or written off as a sign of eating "too much." It isn't. Metabolically healthy individuals generally feel sustained energy after meals, not depletion.
Difficulty losing weight, especially around the abdomen
Insulin is a fat-storage hormone. When levels are chronically elevated, the body is receiving a near-constant signal to store energy rather than burn it. This makes weight loss frustratingly difficult even with caloric restriction and exercise.
Visceral fat, the fat stored deep in the abdomen around the organs is both a symptom and a driver of insulin resistance. A growing waistline, particularly in the absence of significant weight changes elsewhere, is a meaningful early indicator. Waist circumference above 80cm (31.5 inches) in women and 94cm (37 inches) in men is associated with increased metabolic risk regardless of overall body weight.
Insulin is a fat-storage hormone. When levels are chronically elevated, the body is receiving a near-constant signal to store energy rather than burn it. This makes weight loss frustratingly difficult even with caloric restriction and exercise.
Visceral fat, the fat stored deep in the abdomen around the organs is both a symptom and a driver of insulin resistance. A growing waistline, particularly in the absence of significant weight changes elsewhere, is a meaningful early indicator. Waist circumference above 80cm (31.5 inches) in women and 94cm (37 inches) in men is associated with increased metabolic risk regardless of overall body weight.
Skin changes: Acanthosis Nigricans and Skin Tags
The skin often reflects what's happening metabolically before lab tests do.
Acanthosis nigricans is a darkening and thickening of the skin that typically appears in body folds the back of the neck, armpits, groin, and under the breasts. The patches feel velvety to the touch and are darker than the surrounding skin. They are not a rash or a hygiene issue; they are a direct response to elevated insulin stimulating skin cell growth.
Skin tags small, soft, benign growths that appear on the neck, armpits, eyelids, or under the breasts are also strongly associated with insulin resistance and hyperinsulinaemia, and frequently appear years before any glucose abnormality.
The skin often reflects what's happening metabolically before lab tests do.
Acanthosis nigricans is a darkening and thickening of the skin that typically appears in body folds the back of the neck, armpits, groin, and under the breasts. The patches feel velvety to the touch and are darker than the surrounding skin. They are not a rash or a hygiene issue; they are a direct response to elevated insulin stimulating skin cell growth.
Skin tags small, soft, benign growths that appear on the neck, armpits, eyelids, or under the breasts are also strongly associated with insulin resistance and hyperinsulinaemia, and frequently appear years before any glucose abnormality.
Hormonal disruption in women
Insulin has a powerful influence on reproductive hormones. In women, chronically elevated insulin stimulates the ovaries to produce excess androgens (male hormones), which underlies much of the hormonal chaos seen in polycystic ovary syndrome (PCOS).
Signs of androgen excess that may indicate underlying insulin resistance include:
Irregular or absent menstrual cycles
Excess facial or body hair (hirsutism)
Hair thinning or loss from the scalp
Acne, particularly along the jawline and chin
Difficulty conceiving
PCOS is now understood to be, in large part, a metabolic condition driven by insulin resistance and many women with PCOS have completely normal fasting glucose levels.
Insulin resistance also impairs ovulation, which connects directly to conditions like Luteinized Unruptured Follicle Syndrome (LUFS), where the hormonal environment undermines the final steps of the ovulatory process.
Brain Fog and Poor Concentration
The brain is an insulin-sensitive organ. When insulin signalling is impaired, cognitive function often suffers. People describe difficulty concentrating, trouble finding words, a sense of mental heaviness, and what many call "thinking through treacle."
This kind of cognitive sluggishness particularly when it worsens after meals or improves significantly after fasting can be an early signal of metabolic dysregulation well before any formal diagnosis.
Cravings for Sugar and Carbohydrates
Persistent sugar cravings are not simply a matter of willpower or habit. When cells are insulin resistant and glucose isn't being taken up efficiently, the brain receives signals that energy is low even if you've just eaten. This triggers powerful cravings for fast-acting carbohydrates, creating a cycle that worsens insulin resistance over time.
The pattern of needing something sweet after meals, or feeling shaky, irritable, or anxious if meals are delayed, points to poor metabolic flexibility the body's reduced ability to switch between burning glucose and burning fat.
The brain is an insulin-sensitive organ. When insulin signalling is impaired, cognitive function often suffers. People describe difficulty concentrating, trouble finding words, a sense of mental heaviness, and what many call "thinking through treacle."
This kind of cognitive sluggishness particularly when it worsens after meals or improves significantly after fasting can be an early signal of metabolic dysregulation well before any formal diagnosis.
Cravings for Sugar and Carbohydrates
Persistent sugar cravings are not simply a matter of willpower or habit. When cells are insulin resistant and glucose isn't being taken up efficiently, the brain receives signals that energy is low even if you've just eaten. This triggers powerful cravings for fast-acting carbohydrates, creating a cycle that worsens insulin resistance over time.
The pattern of needing something sweet after meals, or feeling shaky, irritable, or anxious if meals are delayed, points to poor metabolic flexibility the body's reduced ability to switch between burning glucose and burning fat.
High Triglycerides and Low HDL Cholesterol
A standard lipid panel can reveal insulin resistance even when glucose is normal. The hallmark pattern is elevated fasting triglycerides (above 1.7 mmol/L) combined with low HDL cholesterol (below 1.2 mmol/L in women, below 1.0 mmol/L in men).
Insulin drives the liver to convert excess glucose into triglycerides, and chronically elevated insulin suppresses HDL production. This lipid pattern sometimes called atherogenic dyslipidaemia significantly raises cardiovascular risk and is one of the earliest measurable metabolic abnormalities in insulin resistance.
Elevated Blood Pressure
Insulin resistance and high blood pressure frequently travel together. Elevated insulin increases sodium retention in the kidneys and activates the sympathetic nervous system, both of which push blood pressure upward. Readings that are creeping toward the higher end of normal or that are formally elevated without a clear explanation can reflect underlying metabolic dysfunction.
Sleep Disruption
Poor sleep both causes and is worsened by insulin resistance. Difficulty falling asleep, frequent night waking, or non-restorative sleep disrupts cortisol and insulin regulation the following day. Conversely, insulin resistance impairs sleep architecture and is strongly linked to obstructive sleep apnoea, which itself worsens metabolic health further.
Poor sleep both causes and is worsened by insulin resistance. Difficulty falling asleep, frequent night waking, or non-restorative sleep disrupts cortisol and insulin regulation the following day. Conversely, insulin resistance impairs sleep architecture and is strongly linked to obstructive sleep apnoea, which itself worsens metabolic health further.
Polycystic Ovaries on ultrasound
Many women are told they have "polycystic ovaries" on ultrasound without being told what this might mean metabolically. The presence of multiple small follicles arranged around the ovary is, in many cases, a direct consequence of insulin-driven androgen excess interfering with normal follicular development and ovulation. It is an ovarian sign of a systemic metabolic problem.
Many women are told they have "polycystic ovaries" on ultrasound without being told what this might mean metabolically. The presence of multiple small follicles arranged around the ovary is, in many cases, a direct consequence of insulin-driven androgen excess interfering with normal follicular development and ovulation. It is an ovarian sign of a systemic metabolic problem.
Why standard testing misses it
The conventional screening tool for blood sugar problems is fasting glucose, sometimes accompanied by HbA1c. Both measure the level of glucose in the blood. Neither measures insulin.
Insulin resistance is defined by elevated insulin in the context of normal (or near-normal) glucose. You cannot detect it by measuring only glucose.
The most informative tests include:
Fasting insulin. A fasting insulin level above roughly 8–10 mIU/L (depending on laboratory reference ranges) suggests the pancreas is working harder than it should to maintain normal glucose, even if glucose itself is normal.
HOMA-IR. The Homeostatic Model Assessment of Insulin Resistance combines fasting glucose and fasting insulin into a single score. A value above 2.0 is generally considered indicative of insulin resistance, though some clinicians use a threshold of 1.5 for earlier identification.
Oral Glucose Tolerance Test with insulin levels. A two-hour OGTT that measures both glucose and insulin responses provides a much richer picture of metabolic health than fasting tests alone.
Fasting triglyceride-to-HDL ratio. A ratio above 1.5 (using mmol/L values) is a practical, inexpensive proxy for insulin resistance that can be derived from a standard lipid panel.
If you suspect insulin resistance, it is worth asking your doctor specifically for fasting insulin alongside the standard glucose tests.
The conventional screening tool for blood sugar problems is fasting glucose, sometimes accompanied by HbA1c. Both measure the level of glucose in the blood. Neither measures insulin.
Insulin resistance is defined by elevated insulin in the context of normal (or near-normal) glucose. You cannot detect it by measuring only glucose.
The most informative tests include:
Fasting insulin. A fasting insulin level above roughly 8–10 mIU/L (depending on laboratory reference ranges) suggests the pancreas is working harder than it should to maintain normal glucose, even if glucose itself is normal.
HOMA-IR. The Homeostatic Model Assessment of Insulin Resistance combines fasting glucose and fasting insulin into a single score. A value above 2.0 is generally considered indicative of insulin resistance, though some clinicians use a threshold of 1.5 for earlier identification.
Oral Glucose Tolerance Test with insulin levels. A two-hour OGTT that measures both glucose and insulin responses provides a much richer picture of metabolic health than fasting tests alone.
Fasting triglyceride-to-HDL ratio. A ratio above 1.5 (using mmol/L values) is a practical, inexpensive proxy for insulin resistance that can be derived from a standard lipid panel.
If you suspect insulin resistance, it is worth asking your doctor specifically for fasting insulin alongside the standard glucose tests.
What you can do
Insulin resistance is not a life sentence. It is one of the most modifiable metabolic conditions there is and lifestyle interventions can produce meaningful improvements within weeks.
Reduce refined carbohydrates and sugar. Cutting back on foods that produce rapid glucose spikes ultra-processed foods, sugary drinks, white bread, pastries directly reduces the insulin burden on your cells.
Prioritise protein and healthy fats. Meals built around adequate protein and fat produce a much smaller insulin response than carbohydrate-heavy meals, and support stable energy throughout the day.
Strength training. Skeletal muscle is the largest site of glucose disposal in the body. Building and maintaining muscle mass through resistance exercise significantly improves insulin sensitivity.
Walk after meals. Even a 10-minute walk after eating measurably reduces post-meal glucose and insulin spikes.
Improve sleep. Addressing sleep quality and duration is not optional,it is foundational to metabolic health.
Manage stress. Chronic psychological stress drives cortisol, which raises glucose and worsens insulin resistance. Stress management is a metabolic intervention, not a luxury.
Consider time-restricted eating. Allowing longer gaps between meals or a defined eating window during the day gives insulin levels a chance to fall and can improve insulin sensitivity over time.
The Bigger Picture
Normal blood sugar is not the same as metabolic health. Insulin resistance can exist, and cause significant harm, long before glucose readings become abnormal. The symptoms described above are the body's early warning system and they are worth taking seriously.
If several of these signs resonate with you, the most important step is to ask for the right tests. Fasting insulin, HOMA-IR, and a full lipid panel are straightforward, inexpensive, and far more informative than glucose alone.
The earlier insulin resistance is identified, the more readily it responds to intervention and the greater the opportunity to protect long-term health before more serious consequences develop.
This article is intended for educational purposes only and does not constitute medical advice. Please speak with a qualified healthcare provider before making changes to your diet, exercise, or medication.
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