If your doctor is checking for diabetes, your request will likely list fasting blood sugar (FBS), HbA1c or both, tests done at our Marulas branch in Valenzuela. They answer two different questions.
In short
- FBS shows your blood sugar now; HbA1c, your 2 to 3 month average.
- FBS usually needs 8 to 12 hours of fasting. HbA1c does not.
- Many doctors order both. Follow your doctor’s request.
The short version
| Fasting blood sugar | HbA1c | |
|---|---|---|
| What it shows | Your blood sugar right now, after fasting | Your average blood sugar over the past 2 to 3 months |
| Fasting needed | Yes, 8 to 12 hours | No |
| Used for | Screening, and checking day-to-day control | Seeing the longer trend and how well treatment is working |
| Can change quickly | Yes. A late dinner or illness can move it | No. It moves slowly |
Fasting blood sugar
FBS measures the sugar in your blood after at least 8 hours without food: a snapshot of one moment. Because food, stress and illness all affect it, your doctor may repeat the test before making a diagnosis.
HbA1c
Sugar in your blood sticks to hemoglobin, the protein in red blood cells, and HbA1c measures how much has stuck. Red blood cells live for about three months, so the result reflects your average over that time.
What the numbers usually mean
These are the cut-offs doctors commonly use. Your doctor makes the diagnosis, often after a repeat test.
| Fasting blood sugar | HbA1c | |
|---|---|---|
| Normal | Below 100 mg/dL | Below 5.7% |
| Prediabetes | 100 to 125 mg/dL | 5.7% to 6.4% |
| Diabetes | 126 mg/dL or higher | 6.5% or higher |
Which one do you need?
Follow your doctor’s request; many order both, FBS for where you are today and HbA1c for the pattern. If you already have diabetes, HbA1c is usually repeated every few months to track your control.
Having these tests at Sunrise
If FBS is on your request, come in the morning after an overnight fast; plain water is fine. FBS results are usually ready the same day, and the front desk can confirm HbA1c availability and release time.
Read our guide on how to prepare for a fasting blood test, see all our laboratory tests, or ask for both as part of a check-up.
Tests mentioned in this article
This article is general information and does not replace advice from your own doctor.
More health guides
Check-ups and consultations · 3 min read
Annual physical exam: what it includes and how to prepare
What a yearly physical exam usually includes, how to prepare, what to bring and when results are ready.
Check-ups and consultations · 3 min read
Employee medical checkups: what they include and why they matter
What a workplace medical checkup usually includes, why it matters for employees and employers, and how to prepare.
Check-ups and consultations · 3 min read
Health screenings for seniors: which tests matter as you age
Which health screenings matter as you age, from blood pressure and blood sugar to cholesterol and kidney tests, and how often to have them.
Call before you come, or just walk in
Our front desk can tell you if your test needs fasting, which doctor is in today, and what your HMO covers.