When Is Insulin Necessary for Gestational Diabetes?

"Do I need insulin now?" is usually the first question that arises once blood glucose values fail to reach the target range despite dietary adjustments. The short answer: not automatically — and if it does come to that, it is not a deterioration but a well-studied, safe next step.

How Often Insulin Is Actually Needed

Depending on the individual risk profile, around 20 to 30 percent of women with gestational diabetes require insulin at some point during the pregnancy, according to the DDG practice recommendation. The large majority therefore reaches target values through diet and exercise alone.

When the Question of Insulin Arises

If dietary changes and physical activity are insufficient, the question of insulin is typically assessed within one to two weeks of starting this first-line therapy — sooner if values are markedly elevated. A practical rule of thumb: if target values are exceeded in more than half of the measurements within a given week, insulin therapy is considered.

Isolated elevated fasting values alone can also be an indication for insulin, even if all other values are within the target range, because the fasting value shows a particularly close association with foetal growth.

Why the Ultrasound Picture Also Plays a Role

One aspect that often comes as a surprise: the decision for or against insulin depends not only on blood glucose values but also on the growth of the baby's abdominal circumference as shown on ultrasound. If the baby is growing in the upper centile range, insulin is started more readily, even with only mildly elevated values. If ultrasound shows unremarkable, appropriately-sized (normosomic) growth, minor exceedances of target values can be tolerated. This link to foetal growth is intended to avoid both over- and under-treatment.

What Insulin Therapy Looks Like in Practice

Treatment usually follows the principle of intensified conventional insulin therapy (ICT), but only basal insulin or only short-acting insulin may be needed, depending on which times of day show elevated values. Starting insulin therapy is generally carried out on an outpatient basis.

What If the Diagnosis Comes Late in the Pregnancy?

According to the guideline, starting insulin therapy shortly before the due date can still be beneficial — among other things to prevent hypoglycaemia in the newborn after delivery.

What Insulin Does Not Mean

Needing insulin for GDM is not a sign of having "done something wrong". Whether someone needs insulin depends on individual insulin resistance and the capacity of the pancreas — both factors that can be influenced, but not fully controlled, by diet and exercise.

Frequently Asked Questions

Do I have to inject insulin, or are there tablets?

In cases of pronounced insulin resistance, metformin may in certain situations be considered as an off-label therapy following medical assessment. This decision is made exclusively by your treating practice on an individual basis.

Do I have to keep taking insulin after the birth?

As a rule, no — the insulin requirement caused by GDM ends with delivery. More on this in the article about the period after birth.

This article does not replace individual medical advice. Whether and which insulin therapy is appropriate for you is decided exclusively by your treating practice.

Sources

Sources (secondary citations from the S3 guideline / DDG practice recommendation):

• Landon MB, Spong CY, Thom E, et al. A multicenter, randomized trial of treatment for mild gestational diabetes. N Engl J Med 2009;361(14):1339–48.
• Crowther CA, Hiller JE, Moss JR, et al. Effect of treatment of gestational diabetes mellitus on pregnancy outcomes (ACHOIS study). N Engl J Med 2005;352(24):2477–86.
• The 20–30% figure for general insulin requirement is a range from the DDG practice recommendation itself, not a single study.