If you have diabetes or are at risk for it, your doctor has likely ordered both a fasting blood sugar test and an HbA1c test at different times. While both are used to assess blood sugar control, they measure very different things — and understanding the distinction helps you take better control of your health.

What Is Fasting Blood Sugar (FBS)?

A fasting blood sugar test measures your blood glucose level at a single point in time, after you have fasted for at least 8 hours (usually overnight). It gives a snapshot of your blood sugar right now.

Normal ranges:

  • Normal: Below 100 mg/dL
  • Pre-diabetes: 100–125 mg/dL
  • Diabetes: 126 mg/dL or higher (on two separate tests)

FBS is often the first test used to screen for diabetes because it is simple, inexpensive, and widely available.

What Is HbA1c?

HbA1c (glycated haemoglobin) measures the percentage of haemoglobin in your blood that has sugar attached to it. Because red blood cells live for about 3 months, this test reflects your average blood sugar level over the past 2–3 months. It does not require fasting.

Normal ranges:

  • Normal: Below 5.7%
  • Pre-diabetes: 5.7%–6.4%
  • Diabetes: 6.5% or higher

For people already diagnosed with diabetes, doctors generally aim for an HbA1c below 7%, though targets may vary based on individual circumstances.

Key Differences

  • Time frame: FBS shows your blood sugar right now; HbA1c shows the average over 2–3 months.
  • Fasting required: FBS requires 8+ hours of fasting; HbA1c does not.
  • Day-to-day variation: FBS can fluctuate based on what you ate yesterday, stress, or illness. HbA1c is more stable and not affected by a single day's meals.
  • Use case: FBS is useful for initial screening and monitoring short-term changes. HbA1c is better for tracking long-term blood sugar control.

Which Test Should You Get?

In many cases, your doctor will order both:

  • FBS is ideal for initial screening, especially during routine health checkups.
  • HbA1c is preferred for diagnosing diabetes, monitoring treatment effectiveness, and understanding long-term trends.

If your FBS is borderline (100–125 mg/dL), an HbA1c test can confirm whether this represents a persistent pattern or just a one-time fluctuation.

Diabetes in Nepal

Diabetes is a growing health concern in Nepal, particularly in urban areas like Kathmandu. Changing diets (more processed and sugary foods), sedentary lifestyles, and increasing obesity are all contributing to a rise in Type 2 diabetes. Many people with pre-diabetes are unaware of their condition, making regular screening essential — especially if you have risk factors like being overweight, having a family history of diabetes, or being over 40.

Key Takeaway: Fasting blood sugar gives you a snapshot of today; HbA1c tells you the bigger picture over the past 3 months. Both tests are valuable, and your doctor may use them together to give the clearest picture of your blood sugar health.

Get both FBS and HbA1c tests at Peoples Diagnostics with same-day results. No appointment needed for fasting blood sugar — just walk in before breakfast. Book online or call 01-4891152.