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Glucose, Fasting

Fasting Blood Sugar

Fasting glucose measures your blood sugar after an overnight fast. It is one of the primary tests for diagnosing diabetes and prediabetes. An 8–12 hour overnight fast is required.

BLOOD24 HOURSFASTING
AEDAED70
  • Free home collection
  • Physician-reviewed report

24 Hours

Turnaround

Blood

Sample

About This Test

What the Glucose, Fasting test tells you

Fasting glucose measures your metabolism at rest. After a genuine overnight fast the sugar in your blood is not arriving from a meal: it is being released by the liver, at a rate that insulin is meant to hold in check. The number is therefore a reading of a quiet negotiation between one organ and one hormone, running in the background while you sleep.

When that negotiation drifts, fasting glucose is often the first thing to move. A liver that has grown less responsive to insulin keeps producing glucose when it should be pausing, and the overnight level creeps upward long before anything is felt. This is why fasting glucose remains a first-line screening test for type 2 diabetes worldwide, and why the intermediate zone between healthy and diabetic is treated as a real finding rather than a near miss: it identifies people for whom changes in eating, weight and activity still alter the trajectory.

The whole value of this test rests on the fast being real. A sweetened coffee, a biscuit, or a shorter fast than you were asked for does not produce a slightly less accurate fasting glucose: it produces a different measurement, one that no interpretive framework was built for. Fasting glucose also feeds the HOMA-IR insulin resistance index when paired with fasting insulin, and it is one component of the metabolic syndrome cluster alongside blood pressure, waist measurement, triglycerides and HDL cholesterol. It is simple, repeatable and inexpensive, but it is one snapshot taken under artificial conditions, and it is normally read together with HbA1c or a post-load measurement rather than alone.

Sample type
Blood
Measured in
mg/dL
Turnaround
24 Hours
Fasting
Required
Best for
Adults at metabolic risk
Why Get Tested?

Routine screening for diabetes in adults, especially those with risk factors like obesity, family history, gestational diabetes, or PCOS.

  • First-line diabetes screening

    It is the standard opening test for type 2 diabetes and prediabetes in adults, particularly where there are risk factors such as excess weight or a family history.

  • Reads the overnight baseline

    Because no food is involved, the value reflects how well insulin restrains the liver's own glucose production: the earliest part of the system to drift.

  • Feeds the resistance index

    Paired with a fasting insulin measurement from the same sample, it produces the HOMA-IR index used to quantify insulin resistance.

  • Highly repeatable over time

    Because conditions are standardised, sequential fasting results are comparable, which makes it a practical way to follow the effect of diet, weight loss or medication.

When This Test Is Ordered

Reasons your doctor may request the Glucose, Fasting test

Your doctor may order this test for any of the reasons below. Some are routine checks, others follow specific symptoms or an earlier result.

  • Screening for diabetes

    • You are being screened for diabetes because of excess weight, a family history, raised blood pressure or an abnormal lipid profile.

  • Symptoms of high blood sugar

    • You have symptoms suggesting high blood sugar such as persistent thirst, frequent urination, unexplained weight loss or blurred vision.

  • Risk factors, medication & follow-up

    • You have polycystic ovary syndrome or a history of glucose intolerance in a previous pregnancy.
    • You are about to start, or are already taking, medication known to raise glucose such as long-term corticosteroids.
    • You have known prediabetes or diabetes and your doctor is following the baseline alongside HbA1c.
Preparation
The short version
A little prep.
  • Blood
  • Free home collection
  • Fasting required
  • Results in 24 Hours
  1. 1
    Book any time

    Pick a morning slot online or on WhatsApp: come fasted per the prep note below.

  2. 2
    We come to you

    A DHA-licensed nurse collects your sample at home or in the office: free home collection.

  3. 3
    Results in 24 Hours

    A physician-reviewed, easy-to-read report lands securely by WhatsApp and email.

Prep note
Physician reviewed

Fasting is required: eat nothing for eight to twelve hours before the sample, and drink only plain water.

That means no tea or coffee even without sugar, no juice, no milk, no chewing gum or mints, and no smoking, all of which can shift the result. Book a morning appointment so the fast falls naturally overnight rather than across a working day, and do not extend it far beyond what was asked, since a very long fast is its own distortion.

Avoid alcohol and strenuous exercise the evening before. Take your usual medicines as prescribed unless your doctor has told you otherwise, but bring the list (including supplements) because corticosteroids, diuretics and diabetes medicines all matter to the interpretation.

Sit quietly for a few minutes before the blood draw, and mention any recent illness or unusually poor night's sleep.

Understanding Your Results

A fasting glucose measures the balance between the liver's overnight glucose output and insulin's restraint of it. A "Normal" mg/dL result is a healthy fasting level, though it says nothing about how you handle food: clearance after a meal can be poor while this value looks fine. A "Prediabetes" mg/dL result is impaired fasting glucose: insulin is working less effectively at the liver and your risk of developing diabetes is raised. A result in the "Diabetes" mg/dL band is consistent with diabetes once confirmed. The figure is only as good as the fast behind it, and an incomplete fast is by far the commonest reason for an unexpectedly high reading. Corticosteroids, thiazide diuretics, infection, injury and surgery all raise it temporarily, and glucose falls in the tube if processing is delayed. Your doctor reads it with your HbA1c, your medication, your symptoms and your history.

SmartReport
100125
Healthy zone85mg/dLNormal
Reference ranges · mg/dL
Normal
Healthy fasting blood sugar.
70–99
Prediabetes
Impaired fasting glucose: increased risk of developing diabetes.
100–125
Diabetes
Consistent with diabetes when confirmed. Consult your physician.
126–300

Ranges are a guide: your physician interprets your result alongside your symptoms and history.

Reading a High or Low Result

  • What a higher result can point to

    • Insulin resistance at the liver, the mechanism behind prediabetes and most type 2 diabetes.
    • Insufficient insulin production, as in type 1 diabetes, chronic pancreatitis, or after pancreatic surgery.
    • Medications including corticosteroids, thiazide diuretics, some antipsychotics and certain immunosuppressants.
    • Acute physiological stress (infection, trauma, surgery, or a cardiac event), which drives glucose up temporarily.
    • Hormonal disorders such as Cushing's syndrome, acromegaly, an overactive thyroid or a phaeochromocytoma.
    • An incomplete fast, which is by far the commonest explanation for an unexpectedly high result.

  • What a lower result can point to

    • Fasting for considerably longer than requested, or missed meals in someone with limited glucose reserves.
    • Glucose-lowering treatment, particularly insulin or sulfonylureas, taken before the sample.
    • Alcohol taken without food the previous evening, which suppresses the liver's overnight glucose output.
    • Adrenal or pituitary insufficiency, advanced liver disease, or severe undernutrition.
    • Rarer causes such as an insulin-secreting tumour or low glucose following bariatric surgery.

These are possibilities, not diagnoses. A single value outside the reference range is interpreted alongside your symptoms, history and other tests: your doctor decides what it means for you.

Limitations & Safety

What this test cannot tell you

  • The result is only as valid as the fast behind it; an interrupted or shortened fast makes the number uninterpretable rather than merely imprecise.
  • It is a single snapshot, and glucose shifts with illness, sleep, acute stress and recent physical activity.
  • It says nothing about how you handle food: a normal fasting value can coexist with markedly poor clearance after a meal.
  • If the sample is not processed promptly, cells continue to consume glucose in the tube and the result falls; a preservative tube limits but does not abolish this.

Risks of the blood draw

  • Mild bruising or brief soreness where the needle went in.
  • Occasional lightheadedness, which settles after a few minutes of rest.
  • Bleeding or infection at the site, which is rare with sterile single-use equipment.
Key Points
  • 1This test requires a genuine overnight fast of eight to twelve hours, with plain water only.
  • 2It measures the balance between the liver's glucose output and insulin's restraint of it, not your response to food.
  • 3It is a first-line screening test, and is usually read together with HbA1c.
  • 4A normal fasting result does not rule out poor glucose handling after meals.
  • 5Any single result is interpreted by your doctor in the context of your symptoms, medication and other tests.
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For a fasting glucose it is best avoided. Caffeine can transiently reduce insulin sensitivity and nudge glucose upward, so plain water is the only safe choice if you want the result to be comparable with previous or future tests.