The key values at a glance
Overview of the central values. Fasting glucose: normal below 100, prediabetes 100 to 125, diabetes from 126 mg/dl (ADA; the WHO sets the lower prediabetes threshold at 110). HbA1c as the long-term value: normal below 5.7 percent, prediabetes 5.7 to 6.4, diabetes from 6.5. Two-hour value in the oral glucose tolerance test: normal below 140, impaired tolerance 140 to 199, diabetes from 200. Time in range from CGM: target more than 70 percent of the time between 70 and 180. Hypoglycaemia: below 70 level 1, below 54 level 2. The values are guideline orientation and do not replace medical assessment.
The key values at a glance
Guideline orientation – lab values belong in medical hands
Value
normal
Precursor
Diabetes
Fasting glucose
mg/dl
< 100
100–125
≥ 126
HbA1c (long-term)
last ~2–3 months
< 5.7%
5.7–6.4%
≥ 6.5%
oGTT 2-Std-Value
glucose load
< 140
140–199
≥ 200
2 h after eating
Everyday
< 140*
Diabetes target < 180
individual
Time in Range
CGM (70–180)
Target > 70%
of the time
in band
Hypoglycaemia
mg/dl
< 70 (level 1)
< 54 (level 2)
help needed
* Healthy usually < 140. Fasting thresholds per the ADA; the WHO sets the lower pre-stage threshold at 110. No self-diagnosis.
Three perspectives on the same metabolism
It becomes easiest when you sort the values by their time perspective – snapshot, everyday and long-term:
Fasting glucose measures the value after several hours without food – a morning assessment. Why it can be elevated despite fasting (the dawn phenomenon) is in Fasting blood sugar & the dawn phenomenon. The oral glucose tolerance test (OGTT) looks at how the body processes a defined amount of sugar – details in OGTT explained.
How much blood sugar rises after meals is shown by the value after eating. Anyone wearing a CGM also sees the Time in Range (TIR) – for me the most honest everyday metric, because it captures the whole day instead of single measurement points.
The HbA1c is the “long-term blood-sugar value” and roughly reflects the last two to three months. It’s central to diagnosis and monitoring – in detail in HbA1c explained. Important: HbA1c and TIR complement each other but don’t replace one another.
When it gets too low: hypoglycaemia
It’s not only high values that count. From below 70 mg/dl we speak of hypoglycaemia (level 1), below 54 mg/dl of a more serious one (level 2). This is mainly relevant for people on insulin or certain tablets – the details and the 15-15 rule are in Recognising hypoglycaemia.
Key takeaways
- Fasting glucose & OGTT = snapshot; post-meal values & TIR = everyday; HbA1c = long-term.
- Diabetes thresholds: fasting ≥ 126, HbA1c ≥ 6.5%, OGTT 2-hour ≥ 200.
- Time in Range (CGM): target usually > 70% between 70 and 180 mg/dl.
- Hypoglycaemia: below 70 (level 1), below 54 (level 2).
- A single value says little – the context counts, interpreted medically.
Sources
Sources as of: 21 Jul 2026.
- Diagnostic thresholds (fasting, HbA1c, OGTT). American Diabetes Association. diabetes.org
- Time in Range international consensus: target > 70% at 70–180 mg/dl. Diabetes Care. care.diabetesjournals.org
- Hypoglycaemia levels (< 70 / < 54 mg/dl); standards of care. ADA. diabetesjournals.org