A normal fasting blood sugar is below 100 mg/dL, and a normal 2-hour post-glucose value is below 140 mg/dL. Diabetes is diagnosed at a fasting value of 126 mg/dL or above, or a 2-hour value of 200 mg/dL or above.
The gap between those two sets of numbers is where prediabetes sits – and it is where most people are first detected, usually without any symptoms at all.
This guide sets out the full chart, explains what each test measures, and shows why fasting sugar alone can miss a problem that a post-meal reading would have caught.
The Chart: Cutoffs Used in India
The Indian Council of Medical Research’s standard treatment workflow for type 2 diabetes uses these thresholds:
| Test | Normal | Prediabetes | Diabetes |
|---|---|---|---|
| Fasting plasma glucose (after 8 hours) | Below 100 mg/dL | 100–125 mg/dL (impaired fasting glucose) | 126 mg/dL or above |
| 2-hour plasma glucose on OGTT | Below 140 mg/dL | 140–199 mg/dL (impaired glucose tolerance) | 200 mg/dL or above |
| HbA1c | Below 5.7% | 5.7–6.4% | 6.5% or above |
| Random plasma glucose | – | – | 200 mg/dL or above, with diabetes symptoms |
A random value of 200 mg/dL or above counts towards diagnosis only when diabetes symptoms are present. Without symptoms, it prompts a confirmatory fasting or OGTT test.
One result is not a diagnosis. Unless symptoms are clearly present, an abnormal result is usually confirmed with a repeat test before diabetes is diagnosed.
What Each Test Actually Measures
Fasting plasma glucose (FPG)
Your blood sugar after at least 8 hours without food. It reflects how well your body keeps glucose in range at rest, mostly a measure of liver glucose output and background insulin function. It is the most commonly ordered sugar test, and the easiest to arrange.
Post-prandial or 2-hour post-glucose
Measured 2 hours after a meal (post-prandial) or 2 hours after a standard 75 g glucose drink (the oral glucose tolerance test, or OGTT). It reflects how efficiently your body clears a glucose load – the first thing to deteriorate in developing type 2 diabetes.
Note the distinction: a PPBS taken 2 hours after your own breakfast is not the same as a formal OGTT, where the glucose load is standardised. The OGTT is the more accurate of the two, which is why guidelines specify it for diagnosis.
HbA1c
Glycated haemoglobin reflects your average blood sugar over roughly the previous three months. It needs no fasting and is not thrown off by what you ate yesterday. It is the single best measure of overall control, and it is also the test most often left out of cheaper panels.
Random plasma glucose
A reading at any time, regardless of meals. Useful as a quick check, but too variable to diagnose on its own unless the value is high and symptoms are present.
Why Fasting Sugar Alone Can Miss It
This is the most useful thing to understand about blood sugar testing.
In developing type 2 diabetes, the body’s ability to handle a glucose load usually deteriorates before its fasting control does. A person can have a perfectly normal fasting value of 95 mg/dL and a 2-hour post-glucose value of 180 mg/dL – clearly in the prediabetes range – and be told their sugar is fine because only the fasting test was done.
This pattern, impaired glucose tolerance with normal fasting glucose, is well recognised and is one reason the oral glucose tolerance test is described in guidelines as the most accurate assessment.
Practical takeaway: if you have risk factors and your fasting sugar is normal, ask your doctor whether a post-meal value or an HbA1c would add anything. Often it does.
How Common Is This in India?
The ICMR-INDIAB study, published in The Lancet Diabetes & Endocrinology in 2023, assessed over 1.1 lakh adults across 31 states and union territories. It found:
- Diabetes in 11.4% of adults
- Prediabetes in 15.3% of adults
Commentary on the study estimated roughly 136 million people in India with prediabetes – a group where lifestyle change can delay or prevent progression to type 2 diabetes. Prediabetes has no symptoms. It is found almost exclusively through testing.
Who Should Get Tested
ICMR recommends screening for adults who are overweight or obese with one or more of these risk factors:
- A first-degree relative with diabetes
- History of cardiovascular disease
- Blood pressure of 140/90 mmHg or above
- Dyslipidaemia (abnormal cholesterol or triglycerides)
- Physical inactivity
- PCOS
- Signs of insulin resistance, such as acanthosis nigricans
- Age over 30
- Previous gestational diabetes
Note that the BMI threshold for Asian Indians is lower than the international one. A BMI of 23 kg/m² already counts as overweight in this population.
Testing is also advised for anyone with osmotic symptoms (excessive thirst, frequent urination), unexplained weight loss, recurrent or deep-seated infections, or non-healing ulcers.
In pregnancy: all pregnant women should have fasting glucose screening in the first trimester, with a 75 g OGTT at 24 to 28 weeks if the first result is normal. Women who had gestational diabetes should be retested 6 weeks after delivery, then every 3 years.
Symptoms of High Blood Sugar
Early type 2 diabetes is frequently silent. When symptoms appear, the common ones are:
- Excessive thirst
- Frequent urination, especially at night
- Unexplained weight loss
- Persistent tiredness
- Blurred vision
- Slow-healing cuts or recurrent infections
- Tingling or numbness in the hands or feet
By the time these appear, blood sugar has usually been raised for some time. This is the argument for testing on risk, not on symptoms.
How to Prepare for a Blood Sugar Test
- Fasting test: 8 hours without food. Plain water is allowed and helps.
- Don’t extend the fast unnecessarily. A 16-hour fast does not give a “better” reading and can distort it.
- Post-prandial test: start the 2-hour clock from the first bite of the meal, not the end.
- OGTT: plan for about 2 hours at the centre, since blood is drawn before and after the glucose drink. Stay seated and avoid walking around, smoking or eating during the wait.
- Take regular medicines unless your doctor advises otherwise, and tell the lab what you take.
- Avoid a sudden diet change before the test. Eating unusually little for two days before testing distorts the result and hides the real picture.
- Reschedule if acutely unwell, since infection and illness temporarily raise blood sugar.
Monitoring Once Diagnosed
For people already diagnosed, the ICMR workflow describes:
- Blood glucose (fasting and 2-hour post-prandial) monthly
- HbA1c every 6 to 12 months, or every 3 months if control is poor
- Annually: ECG, urine albumin-to-creatinine ratio, dilated eye examination, foot examination
Your doctor sets the actual schedule based on your control and other conditions.
What Improves These Numbers
For people in the prediabetes range, the evidence for lifestyle change is strong:
- Reduce refined carbohydrate and sugar, especially sweetened drinks
- Increase fibre from whole grains, pulses, vegetables and fruit
- Add resistance training alongside walking, since muscle is a major site of glucose disposal
- Lose excess weight, particularly abdominal fat
- Improve sleep, since short sleep worsens glucose handling
- Walk after meals, which blunts the post-meal glucose rise
Because HbA1c reflects three months, retesting it earlier than about 3 months after a change will not show the full effect.
Frequently Asked Questions
1. What is a normal blood sugar level?
A normal fasting plasma glucose is below 100 mg/dL and a normal 2-hour post-glucose value is below 140 mg/dL. Normal HbA1c is below 5.7%. Values above these but below the diabetes thresholds fall into the prediabetes range.
2. What is a normal fasting blood sugar range?
Below 100 mg/dL is normal. A fasting value of 100 to 125 mg/dL is impaired fasting glucose, a form of prediabetes, and 126 mg/dL or above meets the threshold for diabetes, usually confirmed with a repeat test.
3. What should blood sugar be 2 hours after eating?
Below 140 mg/dL is normal on a 2-hour post-glucose measurement. A value of 140 to 199 mg/dL indicates impaired glucose tolerance, and 200 mg/dL or above meets the diabetes threshold. A post-meal reading after your own food is less standardised than a formal glucose tolerance test.
4. Can I have normal fasting sugar and still have prediabetes?
Yes. The ability to clear a glucose load often deteriorates before fasting control does, so someone can have a normal fasting value with a raised 2-hour value. This is why the oral glucose tolerance test is described in guidelines as the most accurate assessment.
5. Which is better, fasting sugar or HbA1c?
They answer different questions. Fasting glucose is a single point in time; HbA1c reflects average blood sugar over roughly three months and needs no fasting. Most doctors use them together, and HbA1c is particularly useful for tracking control over time.
6. What is the normal HbA1c level?
Below 5.7% is normal, 5.7 to 6.4% indicates prediabetes, and 6.5% or above meets the threshold for diabetes. Because HbA1c reflects about three months of blood sugar, it does not change meaningfully within a few weeks.
7. How long should I fast before a blood sugar test?
Eight hours is the standard fasting period for a fasting plasma glucose. Plain water is allowed. Fasting far longer than required does not improve the result and can distort it, so an overnight fast with an early-morning slot is the practical approach.
8. Does one high sugar reading mean I have diabetes?
Usually not. Unless clear diabetes symptoms are present, an abnormal result is normally confirmed with a repeat test. A single raised value can also follow illness, acute stress, steroid medication or a very recent meal before a supposedly fasting test.
9. What is prediabetes and can it be reversed?
Prediabetes means blood sugar is above normal but below the diabetes threshold. Indian survey data found it in 15.3% of adults. Many people in this range can delay or prevent progression to type 2 diabetes through diet, weight loss and regular activity, which is why early detection matters.
10. Who should get screened for diabetes in India?
ICMR advises screening adults who are overweight or obese with one or more risk factors: a first-degree relative with diabetes, cardiovascular disease, blood pressure of 140/90 or above, abnormal lipids, physical inactivity, PCOS, signs of insulin resistance, age over 30, or previous gestational diabetes. The overweight BMI threshold for Asian Indians is 23 kg/m².
11. How often should blood sugar be tested once diagnosed?
The ICMR workflow describes fasting and post-prandial glucose monthly, and HbA1c every 6 to 12 months, or every 3 months if control is poor. Annual checks include ECG, urine albumin-to-creatinine ratio, eye examination and foot examination. Your doctor sets the schedule.
12. Can blood sugar tests be done at home in Pune?
Yes. Samples for fasting glucose, post-prandial glucose and HbA1c can be collected at home, and Fittr Labs offers home sample collection in Pune. A formal oral glucose tolerance test needs a centre visit, since it requires a standard glucose drink and a second sample two hours later.
