Insulin
Insulin level after an overnight fast. High insulin with normal sugar is insulin resistance — the stage before diabetes, and common in PCOS
Also known as Fasting insulin, Serum insulin, Insulin resistance, Insulin — Fasting, Insulin Fasting
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- Reports within
- 8 hours
- Parameter included
- 01see list
- Sample
- Blood
- Fasting
- 10 hours
- Measures
- Insulin in the blood after a fast
- Identifies
- Insulin resistance, prediabetes, causes of low sugar
Collected at home
A trained phlebotomist visits at a time you pick, from the next hour
Sealed single-use kit
Opened in front of you, and carried to the lab under controlled conditions
Report within 8 hours
On WhatsApp and email, with any value outside the normal range highlighted
What is the Insulin test?
Fasting insulin measures the hormone your pancreas is producing after an overnight fast, when blood sugar should need very little of it. Insulin moves glucose from the blood into muscle, fat and liver cells.
When those cells stop responding, the pancreas makes more insulin to force the sugar in. Blood glucose stays normal for years while insulin climbs. That is insulin resistance, the stage before type 2 diabetes, and a high fasting insulin with a normal fasting sugar is its earliest signal, long before HbA1c changes. It is common in PCOS, in people with a large waist, fatty liver or high triglycerides. Doctors also pair it with fasting glucose to calculate HOMA-IR, and use it to investigate unexplained low sugar, where an unusually high insulin points to an insulinoma. A low insulin with high sugar means the pancreas is running out, as in type 1 or long-standing type 2 diabetes.
Fast for 10 hours and book a morning slot. The phlebotomist collects the sample at home and the report arrives on WhatsApp and email in 8 hours.
Insulin parameters1 measured
Insulin, fasting
2.6–24.9 µIU/mL
The hormone that moves sugar into cells, measured after fasting, high when the body resists insulin as in pre-diabetes or polycystic ovaries, low in advanced diabetes
Reference ranges are the lab's defaults for adults and are printed on the report beside every value
How to prepare
- Fast for 10 hours before the sample; only water is allowed.
- Book an early-morning slot and give the sample before breakfast and before any diabetes medicine.
- Avoid alcohol and strenuous exercise for 24 hours before.
- If you take biotin (vitamin B7) supplements, stop them 2 days before, with your doctor's agreement.
Who should take it
Women with PCOS, irregular periods or difficulty conceiving. Adults with a waist above 90 cm (men) or 80 cm (women), fatty liver on ultrasound, high triglycerides or low HDL. Anyone with prediabetes, a strong family history of diabetes, or dark velvety skin at the neck or armpits (acanthosis nigricans). People with episodes of shaking, sweating and confusion that improve with food. People with long-standing type 2 diabetes whose doctor is deciding whether to start insulin. Repeat as advised, usually every 6 to 12 months while lifestyle changes are under way.
Before the visit
Tell your doctor about metformin, insulin, sulfonylureas, steroids, oral contraceptives and biotin, all of which change the value. If you inject insulin, the test measures that too, so it is usually paired with a C-peptide test.
Why take the Insulin test?
- Earliest diabetes warning: Insulin rises years before sugar does.
- PCOS: Insulin resistance drives irregular periods, acne and weight gain in most women with PCOS.
- Fatty liver and belly fat: Both are usually insulin-driven, and the test confirms it.
- Unexplained low sugar: A high insulin during hypoglycaemia points to an insulin-producing tumour.
- Type 2 on treatment: Shows whether the pancreas still makes insulin, which helps decide between tablets and insulin injections.
Questions about the Insulin test
What is the fasting insulin test used for?
It measures how much insulin your pancreas is producing after an overnight fast. A high level with normal sugar means insulin resistance, the stage before type 2 diabetes and a common driver of PCOS and fatty liver. It is also used to investigate unexplained low blood sugar.
Do I need to fast for a fasting insulin test?
Yes, fast for 10 hours before the sample; only water is allowed. Book an early-morning slot and give the sample before breakfast and before any diabetes medicine. Avoid alcohol and hard exercise for 24 hours before.
What sample is taken and how does home collection work?
A small blood sample from a vein in the arm. A trained phlebotomist comes to your home with a sealed single-use kit, draws the sample in a few minutes, and carries it to the lab.
What is the normal range for fasting insulin?
The report gives one value, fasting insulin in µIU/mL, with a reference range of 2.6 to 24.9 µIU/mL. Many doctors consider values in the upper half of that range a sign of early insulin resistance, especially when read with fasting glucose as HOMA-IR.
What does a high or low fasting insulin mean?
High insulin with normal or slightly raised sugar means your cells are resisting insulin and the pancreas is overworking, which is insulin resistance. A very high insulin during an episode of low sugar can point to an insulinoma. Low insulin with high sugar means the pancreas is failing, as in type 1 or long-standing type 2 diabetes.
Who should get a fasting insulin test and how often?
Women with PCOS or irregular periods, adults with a large waist, fatty liver, high triglycerides or prediabetes, anyone with dark velvety skin at the neck, and people with unexplained episodes of shaking and sweating relieved by food. It is usually repeated every 6 to 12 months while weight loss or medication is under way.
How long does the fasting insulin report take?
The report reaches you on WhatsApp and email in 8 hours from the time the phlebotomist collects the sample at your home. Book a morning slot and you will usually have it the same day.
Can fasting insulin diagnose diabetes?
No. Diabetes is diagnosed on glucose and HbA1c, not insulin. Fasting insulin tells you what is happening earlier, when sugar is still normal but the pancreas is straining. If your doctor suspects diabetes, a fasting sugar, PPBS or HbA1c is the right test.
Should I stop metformin before the fasting insulin test?
Do not stop it on your own. Metformin lowers insulin resistance and will influence the value, but your doctor may want to see your level on treatment. Take your morning dose after the sample instead of before it, and tell the phlebotomist and your doctor what you take.
Commonly tested together
Often on the same prescription
What happens after you book
- A phlebotomist is assigned and reaches you in your chosen slot, as soon as the next hour
- The sample is collected with a sealed single-use kit and moved on a cold chain
- The report lands on WhatsApp and email within 8 hours