Fasting Glucose in Pregnancy — What It Means
Informational only. Antenatal results should always be discussed with your obstetrician, who interprets them for your specific pregnancy.
Fasting glucose measures the sugar in your blood. It is taken after an overnight fast of at least 8 hours. Pregnancy hormones make your body respond less well to insulin. Finding raised fasting sugar early lets your team act in good time. This supports a healthy pregnancy for you and your baby.
First trimester · Second trimester
Last reviewed: 2026-08-16
When is it done?
You often have this at your first antenatal visit to set a baseline. It is done again around 24 to 28 weeks. That check is part of testing for pregnancy diabetes.
Why is it done in pregnancy?
Pregnancy hormones make your body respond less well to insulin. Finding raised fasting sugar early lets your team act in good time. This supports a healthy pregnancy for you and your baby.
Trimester-specific ranges
Trimester 1
Fasting plasma glucose ≥ 92 mg/dL (5.1 mmol/L) at any gestational age meets the WHO/IADPSG threshold for gestational diabetes mellitus
Sources: [WHO / IADPSG, 2013]
Trimester 2
Fasting plasma glucose ≥ 92 mg/dL (5.1 mmol/L) on a 75 g OGTT meets the WHO/IADPSG threshold for gestational diabetes mellitus
Sources: [WHO / IADPSG, 2013]
What to discuss with your obstetrician
Ask your obstetrician if a single fasting sugar or a full glucose tolerance test suits your stage. Also ask what your result means for monitoring or food changes.
Questions to ask your obstetrician
About this result
- What does my Fasting Glucose result mean for me and my baby at this stage of pregnancy?
- Is my Fasting Glucose being read against a pregnancy-specific range?
What to do next
- Based on my Fasting Glucose, is there anything you would suggest I do or change during this pregnancy?
About retesting
- Will my Fasting Glucose be checked again later in the pregnancy, and if so, when?
The bigger picture
- How does my Fasting Glucose fit with the rest of my antenatal checks?
Frequently asked questions
- Is a fasting glucose test the same as the gestational diabetes test?
- Fasting glucose is one part of it. It is the first reading in a 75 g oral glucose tolerance test (OGTT). A single fasting result can also raise concern. But the OGTT, with more time points, gives a fuller picture.
- What level of fasting glucose raises concern during pregnancy?
- By WHO/IADPSG rules, a fasting sugar of 92 mg/dL (5.1 mmol/L) or above matters. This applies at any point in pregnancy. It meets the threshold for pregnancy diabetes (gestational diabetes mellitus).
- Do I need to fast for a specific number of hours before this test?
- Yes. You need at least an 8-hour overnight fast for the result to be valid. Any food or sugary drink will make the result invalid.
- Can I have gestational diabetes with a normal fasting glucose?
- Yes. Some women have a normal fasting level. But their 1-hour or 2-hour values on an OGTT are raised. This is why the full OGTT is the standard check, not fasting sugar alone.
- What happens if my fasting glucose is high?
- Your obstetrician will advise on the next steps. These may include a full OGTT if not already done. They may also include food advice, home blood sugar checks, and follow-up visits.
Sources
- WHO / IADPSG (2013) — Diagnostic Criteria and Classification of Hyperglycaemia First Detected in Pregnancy, WHO/NMH/MND/13.2
- FOGSI / DIPSI (2018) — DIPSI (Diabetes in Pregnancy Study Group India) guidelines for management of gestational diabetes mellitus
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