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Fasting Insulin

Can show early insulin resistance before blood sugar or HbA1c rise, sometimes years before a diabetes diagnosis. Requires clinic visit.

INSU
Cardiometabolic
Measured in pmol/L

What it measures

Fasting Insulin measures the amount of the hormone insulin circulating in your blood after a 12-hour fast. Insulin is produced by the beta cells of your pancreas and acts as a master key that unlocks your cells so they can absorb glucose (sugar) from the bloodstream and use it for energy. Measuring insulin in a fasted state can reveal early signs of metabolic imbalance, sometimes years before changes show up on standard blood sugar or HbA1c tests. When your body is working well, a small amount of insulin is sufficient to keep blood sugar neatly controlled.

However, if your cells start becoming less responsive to insulin, a state known as insulin resistance, your pancreas compensates by producing more of it. For a while, this extra insulin keeps blood sugar levels looking perfectly normal on routine tests, but behind the scenes the pancreas is working overtime. Think of it like a thermostat in your home: if the insulation starts deteriorating, the boiler has to fire more frequently to maintain the same temperature. Everything feels fine inside, but the energy bill (your insulin level) tells the real story. Over time, if insulin resistance continues to progress, the pancreas may eventually struggle to keep up, and blood sugar levels begin to rise.

Catching things at the insulin stage, before blood sugar is affected, gives you more time to make lifestyle changes. Your fasting insulin level is influenced by several factors, with diet being one of the most significant, particularly your intake of refined carbohydrates and sugars. Body weight, especially excess fat around the midsection, physical activity levels, sleep quality, stress, and genetics all play important roles. Insulin resistance often responds well to lifestyle changes including regular exercise, dietary adjustments, improved sleep, and weight management. If your fasting insulin is higher than expected, your GP can help you understand the result in context and work with you on a practical plan to support your metabolic health going forward.

What your results mean

Low

Below Range

A low insulin level may indicate that your pancreas is producing less insulin than expected. This can be a normal finding in people who eat a low-carbohydrate diet. If you have any concerns about your blood sugar management, your GP can discuss this in the context of your glucose and HbA1c results.

Normal

Within Range

Your insulin level is within the reference range, which suggests your pancreas is producing an appropriate amount of insulin to manage your blood sugar.

High

Above Range

A raised fasting insulin level suggests your body is producing more insulin than usual to keep blood sugar under control, a pattern known as insulin resistance. Left unaddressed, insulin resistance can progress over time and increase the risk of metabolic conditions including type 2 diabetes. The important thing to know is that insulin resistance is often highly responsive to lifestyle changes, including regular physical activity, reducing refined carbohydrates, improving sleep, and managing weight. Discuss this result with your GP, who can assess your broader metabolic picture and work with you on a plan to address it.

Tests that include Fasting Insulin

See where your Fasting Insulin sits

A blood test that includes Fasting Insulin.

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