Why Hospitals Use Different Cut-offs
Reviewed by CDE Mehandi Sharma · Updated
If two hospitals gave you different answers, or a relative was diagnosed on numbers that look like yours, this is why. There is no single agreed GDM threshold, and the choice changes the result dramatically.
India's national study measured this directly. Applying different criteria to the same population produced these prevalence figures:
| Criteria | Prevalence found |
|---|---|
| DIPSI | 11.4% |
| NICE (used for the study's headline figure) | 22.4% |
| TOBOGM | 28.7% |
| IADPSG | 36.3% |
That is the same women, the same blood, and a threefold difference in how many are told they have GDM.
The approaches differ in whether fasting is required, how much glucose is given, how many blood samples are taken, and where the cut-offs sit. DIPSI uses one non-fasting sample at two hours with a 140 mg/dL cut-off. IADPSG requires fasting and reads three time points with lower thresholds, so it identifies considerably more women.
What this means for you, practically. A diagnosis is real and worth acting on regardless of which criteria produced it. But if you have been tested two different ways with conflicting results, that is a genuine question for your doctor rather than a mistake by either lab.
Ask which criteria your hospital uses, and keep the actual numbers rather than only the conclusion.