Gestational diabetes — gestational diabetes mellitus in medical terms — is a disorder of sugar metabolism that is first detected during pregnancy. Blood sugar is higher than it should be, but usually still below the values that otherwise define overt diabetes.¹
Behind it lies an entirely normal process: from the middle of pregnancy onwards the placenta produces hormones that weaken the effect of the body's own insulin. This insulin resistance leaves more sugar in the blood, which benefits the baby. Normally the pancreas compensates by producing more insulin — if it cannot, blood sugar rises.
A distinction that often causes confusion. Gestational diabetes is not the same as diabetes that was already there beforehand. If a clearly raised value is measured very early on, an undetected type 2 diabetes may be behind it — which matters, because the care during pregnancy and the follow-up afterwards differ.
And one more thing: gestational diabetes is not a personal failing. It arises from hormones, predisposition and metabolism — not from anyone having eaten “too many sweet things”.
2. Why you usually notice nothing
The key feature: gestational diabetes generally causes no symptoms at all. The values are usually not high enough to bring on the typical signs — which is why nobody waits for symptoms and screening is done actively instead.² Where signs do appear, they are non-specific and common in pregnancy anyway:
Strong thirst — excessive thirst and passing urine frequently are an everyday part of pregnancy.
Tiredness and weight changes — tiredness is part of the normal state of things, and a striking weight gain can mean many things.
Sometimes it is something else that shows up first on the ultrasound scan: a baby that is too large or an increased volume of amniotic fluid — both reasons to take a look at blood sugar.
The practical conclusion. Having no symptoms is no proof that everything is fine. Screening is not a formality but the only reliable way to find gestational diabetes in good time — and once it is found, it is usually very treatable.
3. How it develops and who it affects
The cause is the mismatch between the rising need for insulin in the second half of pregnancy and what the pancreas can deliver. Whether it develops depends on factors nobody chose for themselves.³
Family predisposition — type 2 diabetes in parents or siblings raises the risk.
Gestational diabetes in an earlier pregnancy and older age.
Excess weight — obesity is a risk factor, but not a verdict: slim women are affected too.
Glucocorticoids — given to mature the baby's lungs, for example; they push blood sugar up temporarily.
No risk factor does not mean no risk. A substantial share of diagnoses are made in women with no identifiable risk factor. That is why screening is offered to all pregnant women, not only to those with a notable history.
4. Screening: the pre-test and the OGTT
Screening is part of the German maternity care directives (Mutterschafts-Richtlinien) and is therefore covered by the statutory health insurance funds. It is offered between 24+0 and 27+6 weeks of pregnancy — the point at which insulin resistance becomes pronounced.⁴ It runs in two stages:
50 g screening test. You drink a sugar solution, whatever the time of day and whenever you last ate — you do not need to be fasting. A measurement is taken one hour later; if the value is unremarkable, screening ends there.
75 g OGTT. If the pre-test is abnormal, the diagnostic test follows on a different day, fasting for at least eight hours. Measurements are taken fasting and after one and two hours; reaching a single threshold is enough.¹
Test
Measurement
Threshold (venous plasma)
What it means
50 g screening test
after 1 hour
from 135 mg/dl (7.5 mmol/l)
Abnormal — the OGTT follows
50 g screening test
after 1 hour
from 200 mg/dl (11.1 mmol/l)
Diagnosis confirmed
75 g OGTT
fasting
from 92 mg/dl (5.1 mmol/l)
One value is enough
75 g OGTT
after 1 hour
from 180 mg/dl (10.0 mmol/l)
One value is enough
75 g OGTT
after 2 hours
from 153 mg/dl (8.5 mmol/l)
One value is enough
Table scrolls to the right
These values apply to laboratory measurements from venous blood. A handheld meter is not suitable for making the diagnosis — but it is exactly right for monitoring treatment later on (see Understanding blood values).
5. What it means for baby and mother
Being matter-of-fact matters more here than drama: well-treated gestational diabetes generally takes an uneventful course, and the risks below apply above all to values that go untreated. Sugar crosses the placenta to the baby, insulin does not — so the baby produces more insulin of its own, and insulin is a growth hormone.²
Macrosomia — a baby larger than average, which can make the birth more difficult.
Adjustment problems in the newborn — above all low blood sugar in the first hours, which is why the baby's blood sugar is checked. Jaundice is also somewhat more common.
For you: high blood pressure and pre-eclampsia — more common than otherwise, which is why blood pressure checks are part of the care; inductions and caesarean sections also increase, usually because the baby is large.
For you: a markedly raised risk of type 2 diabetes later on — the most important point for afterwards.
The crucial perspective. These are possibilities, not certainties. With well-controlled values the pregnancy usually runs without anything out of the ordinary. A diagnosis means closer monitoring — not automatically a dramatic course.
6. Treatment step 1: diet and exercise
Treatment always begins with a change of diet and with exercise, not with medicines — for the majority of women that is enough. Part of it is qualified dietary advice, ideally at a diabetes centre.¹
First lineChanging your diet — in practical terms
Spread meals out rather than skipping them
Three main meals and two to three small snacks; a late snack helps prevent a high fasting value in the morning. Going hungry is explicitly the wrong approach.
Choose your carbohydrates wisely
Wholegrains, pulses and vegetables raise blood sugar more slowly than white flour. Carbohydrates are not cut out but spread across the day and combined with protein. Liquid sugars such as soft drinks, juices and smoothies act the fastest — water and unsweetened tea are the simplest lever.
Breakfast is the hardest time of day
Insulin resistance is most pronounced in the morning. A lower-carbohydrate breakfast with some protein — wholemeal bread with quark instead of muesli with fruit and juice — improves exactly the value that was abnormal before for many women.
Exercise: the walk after a meal
15 to 20 minutes of brisk walking after your main meals lowers the value noticeably, because muscles take up sugar even without much insulin. Alongside that, moderate activity such as swimming — what is possible for you is something your maternity team will clarify.
What this step can achieve. Diet and exercise are not a side measure here, they are the actual treatment. Whether they are enough shows up within one to two weeks in your own readings — and that is precisely what self-monitoring is for.
7. Measuring your blood sugar yourself
Self-monitoring shapes your daily life more than anything else — and gives you the most reassurance. It answers the question that no general dietary rule can answer: how does your body respond to what you actually eat?
When to measure
The usual pattern is a daily profile of four measurements: fasting after you get up, plus one or two hours after your main meals. The timing is set by the team looking after you — what matters is that you handle it consistently the same way, otherwise the values cannot be compared. With stable values on dietary treatment the frequency of measurement can go down; on insulin it stays higher.
What to aim for
The guideline gives indicative target values for self-monitoring. They are not an exam result but a decision aid: if they are exceeded over several days, that is the signal for the next step in treatment. Your personal target values are always set by the team looking after you.¹
Time of measurement
Indicative target value
What it tells you
Fasting after getting up
below 95 mg/dl (5.3 mmol/l)
The sugar the liver releases overnight — hard to influence through diet and often the value that makes insulin necessary
1 hour after the start of a meal
below 140 mg/dl (7.8 mmol/l)
The peak after eating — this is where the meal and exercise have the strongest effect
2 hours after the start of a meal
below 120 mg/dl (6.7 mmol/l)
Shows how quickly the value comes back down
Table scrolls to the right
Measuring cleanly and recording sensibly
Wash and dry your hands: traces of fruit or hand cream push the value up; any disinfectant must have evaporated.
Wipe away the first drop of blood and do not squeeze — pressing hard mixes in tissue fluid.
Prick the side of your fingertip, alternate fingers, close the test strip container straight away and check the expiry date.
Note down with every value: the time and how it relates to a meal, roughly what you ate, any exercise, and anything unusual such as an infection, stress or a dose of steroids.
The instructions are set out in the guide Measuring blood sugar correctly. It is only with that context that a column of numbers becomes a pattern: “only the breakfast values are high” leads to a different recommendation than “all the values are raised”. How to prepare for the consultation is described in the guide Prepare for a doctor's appointment.
Four measurements a day — without scraps of paper or guesswork
brite keeps your readings, meals and anything unusual together, so the next appointment goes faster.
If the target values are not reached over one to two weeks despite consistent diet and exercise, insulin treatment is started. That is not a failure — in some women the hormonal insulin resistance simply wins out.¹ The ultrasound scan comes into it too: if the baby is growing strikingly fast, treatment tends to be started sooner.
Second lineInsulin — the treatment of choice in pregnancy
Why insulin of all things
Insulin essentially does not cross to the baby and is the best studied option in pregnancy. That is why it is the drug treatment of choice in Germany.
What the treatment looks like
Often a basal insulin in the evening is enough to begin with if only the fasting value is raised; if the values after meals are too high, a short-acting insulin is added at mealtimes. The dose is adjusted on the basis of your readings. The introduction covers injection technique, rotating the injection sites and storage — the basics are in the guide Injecting insulin correctly.
Oral antidiabetic drugs are not the standard in Germany. Tablets such as metformin are not licensed in Germany for gestational diabetes. Their use is only an option in justified individual cases, arranged by a doctor and after you have been informed about off-label use. Never start tablet treatment on your own initiative, and do not stop treatment you are already on without discussing it — the background is in the guide Medications during pregnancy.⁵
Recognising a hypo. On insulin, blood sugar can fall too low. The warning signs are shaking, sweating, a racing heart, ravenous hunger and confusion. Keep fast-acting sugar to hand — glucose tablets or juice — and take a reading afterwards. If consciousness is clouded or there is a seizure, this is an emergency: call the emergency services on 112 straight away.
9. The birth and the time afterwards
Well-controlled gestational diabetes is in itself no reason for a caesarean section, and no reason to induce labour automatically either. The decision is made individually — on the basis of how well controlled the values are, the estimated weight of the baby, any accompanying conditions and the week of pregnancy.²
Where to give birth: if insulin has been needed, a hospital with a paediatric unit is usually recommended.
For the baby: blood sugar is checked in the first hours; putting the baby to the breast early and feeding frequently help prevent a hypo.
For you: the need for insulin usually drops abruptly once the placenta is delivered, which is why insulin treatment is as a rule stopped straight after the birth — on medical instruction.
Follow-up: taking the type 2 risk seriously
In the great majority of women blood sugar returns to normal after the birth. That does not mean the subject is closed, though: having had gestational diabetes points to a markedly raised risk of developing type 2 diabetes in the years that follow.³
A follow-up OGTT six to twelve weeks after the birth. A regular 75 g test, not just a fasting measurement — a disorder often only shows up under the glucose load. This appointment is very often missed; put it in your diary while you are still pregnant.
Checks after that at intervals of one to three years, depending on the findings and your risk factors — plus a check before another pregnancy, because the risk of it happening again is high.
Breastfeeding works in both directions. On current understanding it lowers the mother's risk of type 2 diabetes later on, and for the baby it is associated with a more favourable metabolic profile as well. Hardly any other diagnosis gives you so much advance warning — if you know your risk, you can act years ahead of it.
10. Everyday life with the diagnosis
Set fixed measuring times — always the same interval after a meal. Comparable values are worth more than many values.
Go out for a short walk after eating — 15 to 20 minutes often brings the one-hour value down noticeably.
Do not hide the outliers — a high value after the birthday cake is information, not an offence. Keep all your medicines in one place as well, see Create a medication plan.
Put the follow-up appointment in your diary straight away — six to twelve weeks after your due date. The most important and most frequently forgotten appointment after the birth.
If blood sugar is going to be part of your life for the long term, the everyday questions are covered in the guide Diabetes medications in daily life.
The follow-up appointment almost everyone forgets
Set yourself a reminder for the OGTT after the birth — and keep track of your readings over time.
The test is an offer, not an obligation. It does make sense, though, because gestational diabetes almost always runs without symptoms and this is the only way it is found in time. In Germany the screening between 24+0 and 27+6 weeks of pregnancy is covered by statutory health insurance.
No. Gestational diabetes arises from the interplay of pregnancy hormones, predisposition and metabolism. Excess weight is a risk factor, but slim women are affected too, and many diagnoses are made in women with no identifiable risk factor.
To begin with, a daily profile with four measurements is usual: fasting and after each of the three main meals. With stable values on dietary treatment the frequency can be reduced; on insulin it stays higher. The exact arrangement and your target values are set by the team looking after you.
No. In some women the hormonally driven insulin resistance is so pronounced that diet and exercise alone are not enough. Insulin essentially does not cross to the baby and is as a rule stopped again straight after the birth.
In Germany metformin is not licensed for the treatment of gestational diabetes. Its use is only an option in justified individual cases, arranged by a doctor and after you have been informed about use outside the licence. The standard is insulin.
In the great majority of women blood sugar returns to normal after the birth. The risk of type 2 diabetes later on stays markedly raised, though. That is why a glucose tolerance test is planned for six to twelve weeks after the birth; breastfeeding lowers the risk further.
German S3 guideline on gestational diabetes mellitus (DDG/DGGG, AWMF reg. no. 057-008) — German source. awmf.org
Gesundheitsinformation.de, German Institute for Quality and Efficiency in Health Care (IQWiG): Gestational diabetes. Accessed 2026 — German source. gesundheitsinformation.de
gesund.bund.de, the national health portal of the German Federal Ministry of Health: Gestational diabetes. Accessed 2026 — German source. gesund.bund.de
Federal Joint Committee (G-BA), the body that decides what statutory health insurance covers in Germany: maternity care directives, screening for gestational diabetes. Accessed 2026 — German source. g-ba.de
Embryotox (Charité — Universitätsmedizin Berlin): Insulin and metformin in pregnancy and while breastfeeding. Accessed 2026 embryotox.de
Blood sugar, insulin and appointments under control — with brite
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Medical disclaimer: This article is for general information and does not replace medical advice, diagnosis or treatment. Target values, how often you measure and the point at which insulin treatment is started are always decided individually by the team looking after you; never start or stop a treatment in pregnancy on your own initiative. If you have signs of a severe hypo, reduced movements from your baby, severe headache with visual disturbances or premature contractions, contact your maternity unit immediately or call the emergency services on 112 (emergency services in Germany). Last updated: August 2026.
