Self-Monitoring Blood Glucose: Target Values and Documentation in GDM

After a gestational diabetes diagnosis, self-monitoring of blood glucose quickly becomes a fixed part of daily life — often several times a day, for weeks. For many women, that is precisely the part that feels most like being ill, even when they otherwise feel completely healthy. Knowing what you are actually looking for can make this routine easier to live with.

When to Measure

At the start, the guideline recommends a four-point profile for the first one to two weeks: fasting in the morning, and one to two hours after the start of each main meal. If all values are within the target range during these first weeks, the measurement frequency can be reduced — for example to one daily measurement on a rotation basis, or a four-point profile twice a week. With insulin therapy, more frequent and targeted measurements are usually required again.

The Target Values at a Glance

According to the DDG practice recommendation, the following target ranges apply for plasma-calibrated self-monitoring devices:

• Fasting / before meals: 65 to 95 mg/dl (3.6 to 5.3 mmol/l)
• 1 hour after eating: below 140 mg/dl (7.8 mmol/l)
• 2 hours after eating: below 120 mg/dl (6.7 mmol/l)

Important to know: these values are reference targets. The guideline explicitly states that a single value above the threshold does not automatically have negative consequences for the baby. What counts is the pattern over several days, not an individual measurement.

Why Documentation Is So Important

Your practice does not assess an individual value but the profile over a period of usually around ten days to two weeks. Complete and accurate documentation in a blood glucose diary is therefore not a formality but the basis for every treatment decision — for example whether dietary adjustment alone is sufficient or whether insulin would be beneficial.

Typical Sources of Error

Especially in the first weeks of self-monitoring, small user errors are common: incorrect handling of the test strip, imprecise timing relative to the meal, or a measurement recorded as "fasting" when a small snack had been eaten shortly beforehand. For this reason, the accuracy of your device is checked regularly, not just your values.

What Happens with the Values

Your practice regularly evaluates the profile and decides on that basis whether the current diet-and-exercise strategy is sufficient or needs to be adjusted. Repeated, systematic exceedances of target values are discussed in the next article, which addresses the question of when insulin comes into play.

Frequently Asked Questions

Is CGM (continuous glucose monitoring) standard for GDM?

No, according to the current guideline, CGM is not part of routine care for gestational diabetes.

Do I also need to measure before dinner in the evening?

Not routinely, as a rule, since postprandial values show a clearer association with pregnancy outcomes than additional pre-meal measurements.

This article does not replace individual medical advice. Your personal target values and measurement frequency are determined 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.