Blood Glucose & OGTT (Gestational Diabetes)
Blood glucose tests measure the amount of sugar in your blood. A fasting glucose test is a simple way to detect diabetes, while the oral glucose tolerance test (OGTT) shows how well your body handles a standard dose of sugar. The OGTT is the reference test for gestational diabetes, a form of diabetes that appears during pregnancy.
At YGOPH, fasting glucose is part of routine antenatal care, and women with risk factors, such as overweight, a previous large baby, diabetes in the family or gestational diabetes in a past pregnancy, are offered an OGTT, usually between 24 and 28 weeks. Detected early, gestational diabetes can be controlled, reducing the risks of a very large baby, a difficult birth and low blood sugar in the newborn.
What are blood glucose tests and the OGTT?
For a fasting glucose, a blood sample is taken after at least 8 hours without food. For the 75 g OGTT, a fasting sample is taken first; you then drink a glucose solution within five minutes, and further samples are taken after one and two hours. You stay seated and rested at the laboratory throughout, without eating or smoking, because activity and food change the results.
- Routine antenatal care, at the first visit
- Pregnant women with risk factors, usually at 24–28 weeks
- Excessive thirst, frequent urination or unexplained weight loss
- Follow-up after gestational diabetes, a few weeks after delivery
- Suspected low blood sugar in newborns and sick children
Good to know
Diagnosing gestational diabetes
Using the WHO criteria for the 75 g OGTT, gestational diabetes is diagnosed if at least one value is at or above: fasting 5.1 mmol/L (0.92 g/L), one hour 10.0 mmol/L (1.80 g/L) or two hours 8.5 mmol/L (1.53 g/L). Your doctor will explain your results and, if needed, arrange dietary advice and closer follow-up.
Fasting glucose outside pregnancy
In adults, a fasting glucose below 5.6 mmol/L (1.00 g/L) is usually normal. Values from 5.6 to 6.9 mmol/L (1.00–1.25 g/L) suggest prediabetes, and 7.0 mmol/L (1.26 g/L) or more on two occasions indicates diabetes. The HbA1c test can complete the assessment.
Glucose checks for newborns
Babies of mothers with diabetes, premature and small babies, and sick newborns can develop low blood sugar in the first hours of life. A quick heel-prick test measures their glucose so that the neonatal team can feed or treat them promptly.