Patient's question:
Medical history: Pregnant for six and a half months, all prenatal check-ups have been normal.Previous treatment and effectiveness: All prenatal check-ups have been normal.
Help needed: Could you please clarify whether it is mandatory to draw blood exactly one hour after drinking the glucose solution for the glucose screening test? Is it acceptable to draw blood before or after one hour? Will the results be inaccurate?
Doctor's answer:
Not possible. The glucose screening test measures how quickly your body metabolizes sugar, and it cannot be done immediately.Wikipedia excerpt:
Blood tests are usually taken between weeks 24 and 28 of pregnancy for screening.
Diabetes screening method:
- Fast for 12 hours before the test.
- Dissolve 50 grams of glucose powder in 200ml of water and drink it within 5 minutes.
- Start timing from the first sip.
- Take a blood test 1 hour later to check blood glucose levels.
- A blood glucose level of ≥7.8 mmol/L indicates abnormal glucose screening, requiring further Glucose Tolerance Test (OGTT).
Glucose Tolerance Test (OGTT) method:
- Fast for 12 hours before the test.
- For the screening test, first take a fasting blood glucose test.
- Then, either:
- Add 150ml of 50% glucose injection to 100ml of water, or
- Dissolve 75 grams of glucose powder in 300ml of water.
- Drink it within 5 minutes, starting timing from the first sip.
- Take blood tests at 1 hour, 2 hours, and 3 hours after drinking.
- Normal values are:
- Fasting: 5.6 mmol/L
- 1 hour: 10.3 mmol/L
- 2 hours: 8.6 mmol/L
- 3 hours: 6.7 mmol/L
- If 2 or more of these values meet or exceed the normal range, it can be diagnosed as gestational diabetes.
- If only 1 value is higher than normal, it is diagnosed as abnormal glucose tolerance.
The most important thing:
You must finish drinking the glucose solution and wait for more than one hour before taking the blood test!