Insulin for gestational diabetes
Food and activity keep blood sugar in range for most people with gestational diabetes, but some need medicine as well. In the US, insulin is the recommended medicine in pregnancy because it does not cross the placenta to the baby. Your team teaches you how to give it and sets your dose.
Why some people need it
In pregnancy, hormones make it harder for insulin to work. Most bodies make more insulin to keep up. With gestational diabetes, the body cannot make enough, and blood sugar goes up. ACOG says some people need medicine to reach normal blood sugar even with diet changes and exercise.1
The ADA says this resistance to insulin grows through the second and third trimesters, and drops quickly after the placenta is delivered. It also says that, depending on the group studied, 70 to 85 in 100 people with gestational diabetes (diagnosed with the 3-hour test criteria) keep it in range with food and activity alone.2 So medicine is a common next step, not a rare one.
When medicine is added
| Guideline | What it says |
|---|---|
| ACOG (US) | Diet and exercise first. If that is not enough, medicine. Insulin is the recommended medicine in pregnancy, and it does not cross the placenta.1 |
| ADA (US) | Insulin is the preferred medicine. Metformin and glyburide should not be the first choice, because both cross the placenta to the baby and may not be enough to reach the targets.2 |
| NICE (UK) | Fasting below 7.0 mmol/L (126 mg/dL) at diagnosis: diet and exercise changes first. If targets are not met in 1 to 2 weeks, metformin. Insulin if metformin is not suitable or not enough. Fasting 7.0 mmol/L or above at diagnosis: insulin straight away, with or without metformin.3 |
ACOG and the ADA are US guidelines; NICE is the UK guideline. Your team follows its own plan.
Targets on insulin
The ADA gives the same upper limits with or without insulin, and adds a lower limit when you take insulin:2
| Check | On insulin | Not on insulin |
|---|---|---|
| Fasting | 70–95 mg/dL (3.9–5.3 mmol/L) | Below 95 mg/dL (5.3 mmol/L) |
| 1 hour after a meal | 110–140 mg/dL (6.1–7.8 mmol/L) | Below 140 mg/dL (7.8 mmol/L) |
| 2 hours after a meal | 100–120 mg/dL (5.6–6.7 mmol/L) | Below 120 mg/dL (6.7 mmol/L) |
NICE advises people who take insulin in pregnancy to keep their blood sugar above 4 mmol/L (72 mg/dL).3 Use the targets your clinic gives you. More on blood sugar targets.
Lows: what to know
- The ADA calls a reading below 70 mg/dL (3.9 mmol/L) low. Treat it quickly, because it can get worse fast.4
- The ADA's 15/15 rule: take 15 grams of fast-acting carbs, then check again after 15 minutes.4 Ask your team what to keep with you and when to call them.
- A severe low, when you need someone else's help to treat it, is an emergency. If a person is unconscious and glucagon is not available, call 911 right away.4
Day to day
- Your ob-gyn teaches you how to give yourself insulin. Keep checking your blood sugar and keep a record to bring to your visits.1 In First Fork, each meal entry has a reading, a note and a medication, so the dose sits next to the number it goes with.
- After the birth: NICE says people with gestational diabetes should stop their blood sugar medicine straight after the birth.3 You still need a follow-up test: see does gestational diabetes go away.
Questions
Is insulin safe for my baby?
Insulin is the recommended medicine for gestational diabetes in the US. ACOG says it does not cross the placenta, so it does not affect the baby.
Does needing insulin mean I failed my diet?
No. ACOG says some people need medicine to reach normal blood sugar even with diet changes and exercise.
Why not metformin pills instead?
The ADA says metformin and glyburide should not be the first choice in pregnancy, because both cross the placenta and may not be enough. In the UK, NICE offers metformin before insulin. Your team decides.
What blood sugar is too low on insulin?
The ADA calls a reading below 70 mg/dL (3.9 mmol/L) low. NICE advises staying above 4 mmol/L (72 mg/dL). Ask your team for your own plan.
Will I need insulin after the baby is born?
NICE says people with gestational diabetes should stop their blood sugar medicine straight after the birth. A follow-up test comes later.
Sources
- ACOG. Gestational Diabetes (FAQ 177, reviewed April 2026). https://www.acog.org/womens-health/faqs/gestational-diabetes
- American Diabetes Association. 15. Management of Diabetes in Pregnancy: Standards of Care in Diabetes—2026. Diabetes Care 2026;49(Suppl. 1):S321. https://pmc.ncbi.nlm.nih.gov/articles/PMC12690181/
- NICE guideline NG3. Diabetes in pregnancy: management from preconception to the postnatal period (recommendations). https://www.nice.org.uk/guidance/ng3/chapter/Recommendations
- American Diabetes Association. What You Need to Know About Low Blood Glucose (Hypoglycemia). https://diabetes.org/living-with-diabetes/treatment-care/hypoglycemia
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