Enter your 50 g screening, 75 g or 100 g diagnostic test results and compare them with the cut-offs used by different organizations.
Screening for gestational diabetes is done between weeks 24 and 28, when pregnancy-related insulin resistance rises markedly (UpToDate, 2026). The Turkish Ministry of Health high-risk pregnancy guideline also recommends either the 50 g screening test or the 75 g tolerance test at 24–28 weeks (Turkish Ministry of Health, 2026).
Screening is done at the first visit if BMI is 25 or more (23 or more in people of Asian origin) together with at least one of: a first-degree relative with diabetes, cardiovascular disease, blood pressure of 130/80 mmHg or more or blood pressure medication, HDL cholesterol below 35 mg/dL and/or triglycerides above 250 mg/dL, polycystic ovary syndrome, physical inactivity, a previous baby of 4000 g or more, gestational diabetes in a previous pregnancy, or other conditions linked to insulin resistance (such as severe obesity, acanthosis nigricans or fatty liver disease). In early screening, fasting glucose of 126 mg/dL or more, random glucose of 200 mg/dL or more or HbA1c of 6.5% or more suggests diabetes present before pregnancy (overt diabetes). If values are below these limits, the Turkish Ministry of Health guideline recommends a 75 g or two-step glucose tolerance test at the first visit, repeated at 24–28 weeks if normal (Turkish Ministry of Health, 2026). ADA, by contrast, advises that the cut-offs set for 24–28 weeks should not be used in the first half of pregnancy (ADA, 2026).
One-step 75 g test (fasting, 1 hour and 2 hours): a single value at or above the cut-off is enough for diagnosis.
| Organization | Fasting | 1 hour | 2 hours |
|---|---|---|---|
| IADPSG / ADA (2026) and Turkish Ministry of Health (2026) | ≥92 mg/dL | ≥180 mg/dL | ≥153 mg/dL |
| WHO (2013 criteria) | 92–125 mg/dL | ≥180 mg/dL | 153–199 mg/dL |
| NICE (NG3) | ≥5.6 mmol/L (100 mg/dL) | — | ≥7.8 mmol/L (140 mg/dL) |
Under WHO criteria, fasting glucose of 126 mg/dL or more or a 2-hour value of 200 mg/dL or more is classed as “diabetes mellitus in pregnancy” rather than gestational diabetes.
Two-step test:
| Step | Cut-off | Meaning |
|---|---|---|
| Step 1: 50 g screen (no fasting needed), 1 hour | ACOG: ≥130, ≥135 or ≥140 mg/dL (chosen by the institution); Turkish Ministry of Health: ≥140 mg/dL | If positive, a 100 g test is done on another day. Under the Turkish guideline, ≥180 mg/dL is treated as diabetes without further testing. |
| Step 2: 100 g, 3-hour test | Carpenter-Coustan: fasting ≥95, 1 h ≥180, 2 h ≥155, 3 h ≥140 mg/dL. NDDG: 105 / 190 / 165 / 145 mg/dL | Diagnosis if at least two values meet or exceed the cut-off. |
Turkey uses the Carpenter-Coustan values for the 100 g test (Turkish Ministry of Health, 2026).
Organizations take different routes: IADPSG, WHO, NICE and FIGO use the one-step approach; ACOG uses the two-step approach; ADA accepts either (UpToDate, 2026). The Turkish Ministry of Health also accepts both tests (Turkish Ministry of Health, 2026).
In a meta-analysis of randomized trials, the one-step approach diagnosed twice as many people (16.3% vs 8.3%), with no clear difference in outcomes such as large babies, cesarean birth, high blood pressure in pregnancy or stillbirth. In the same analysis, twice as many people received glucose-lowering medication with the one-step approach (7.1% vs 3.8%), and low blood sugar in newborns was somewhat more common (9.3% vs 7.6%). UpToDate concludes from these findings that the evidence may favor the two-step approach; ADA recommends the one-step IADPSG criteria because they are the only ones based on pregnancy outcomes (UpToDate, 2026; ADA, 2026).
If gestational diabetes is diagnosed, nutrition therapy and blood glucose monitoring start first, and medication is added if targets are not met. Treatment reduces the risk of a large baby and shoulder dystocia, and possibly preeclampsia (UpToDate, 2026). The Turkish Ministry of Health guideline advises referral to a perinatologist, internist or endocrinologist when two values or the fasting value are high.
After gestational diabetes, a 75 g test is done 4–12 weeks after birth; after that, ADA advises screening every 1–3 years and UpToDate at least every three years. See the gestational diabetes clinical guide for details.
Between weeks 24 and 28. People with a BMI of 25 or more plus an additional risk factor are also screened at the first visit (Turkish Ministry of Health, 2026).
Fasting below 92 mg/dL, 1 hour below 180 mg/dL and 2 hours below 153 mg/dL. If any one value meets or exceeds its cut-off, gestational diabetes is diagnosed (ADA, 2026; Turkish Ministry of Health, 2026).
Under the Turkish guideline, below 140 mg/dL is normal; at 140 or more a 100 g test follows, and at 180 or more diabetes is diagnosed directly. ACOG allows a cut-off of 130, 135 or 140 mg/dL.
Not for the 50 g screening test. For the 75 g and 100 g tests, fast overnight for at least 8 hours (ideally 10 hours).
No serious harm to mother or baby has been linked to the screening or diagnostic tests. The very sweet drink can cause nausea and vomiting in some people (UpToDate, 2026).
If the 24–28 week test is normal, UpToDate does not recommend routinely repeating it later in pregnancy. If an early-pregnancy screen is normal, the test is repeated at 24–28 weeks.
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