High blood sugar levels with gestational diabetes

High blood sugar levels are where your blood sugar levels go over YOUR test target. So that is anything 0.1mmol/l over your target e.g. if your target is 7.8mmol and you get 7.9mmol/l, this is classed as an over-target reading or high blood sugar level.

Bearing in mind that test targets vary all over the UK and Ireland, what is classed as a high reading for one person, maybe still within target levels for someone else.

high blood sugar levels

What to do if you get high blood sugar levels

Re-test your blood sugar levels

Re-wash your hands in just water and re-test your blood sugar levels. It is very easy to touch something, even your face or hair and contaminate your hands before testing. Many soaps and sanitisers can have ingredients which leave residue on the skin which can give falsely high readings and so it is important to wash hands in just water before re-testing.

If levels are still high after re-testing

Record all the results so that your diabetes team can review them and what you ate so that you can review what may have caused the spike in your blood sugar levels.

Drink plenty of water to help flush the sugars through

Move (walk or dance) or be as active as possible for 20 mins or longer. Drinking water helps to flush excess sugars from the body and exercise has an insulin-type effect on the body.

Communicate with your team

Each diabetes team may give different recommendations as to when to contact them, but the general guidance given and also what we recommend is to contact your team after 3 over-target readings within a week.

Don’t wait until your next scheduled appointment if you’re getting over-target readings, give your team a call to discuss it with them.

Some teams will ask you to come in earlier to start medication or insulin, others may fax a prescription through to your GP surgery or Pharmacy for you to collect and start. Other teams may say that they will review your readings when you next attend the clinic.

Never be afraid to contact your team to discuss things with them. They are there to help, support and advise you.

Be wary that in many hospitals, there is not normally a diabetes specialist midwife or nurse available out of hours, at the weekends, or on holidays (unless you have been given a mobile number). So if you have been having higher readings towards the end of the week, give yourself plenty of time to get in touch with them.

Are high blood sugar levels bad?

High blood sugar levels (levels over your target) mean that excess glucose is in the bloodstream that cannot be processed due to being insulin resistant (diabetic) and the excess glucose is being passed through to the baby.

In response to this excess glucose, the baby increases their own insulin production and with insulin being a growth hormone, this can result in excessive growth of the baby.

The excess sugar can cause many different complications in the baby, some of which can be fatal if blood sugar levels are not controlled. To read more about the complications high blood sugar levels can cause, please read more here.

large growth

Why are targets lower for gestational diabetes than for diabetics who are not pregnant?

A common question that comes up, is why are the targets used for gestational diabetes so much lower than that used for other types of diabetes. The answer is simply that the targets used for diabetes during pregnancy are targets that have been proven by evidence-based research to have a beneficial impact on the baby and related complications.


You may experience some symptoms when you have high blood sugar levels which suggest you are hyper. Symptoms may include the following:

  • feeling thirsty
  • passing urine more frequently
  • headaches
  • lethargy
  • abdominal pain
  • shaking
  • sweating
  • heart racing

The symptoms of hyposfalse hypos (low blood sugar levels) and hypers can be very similar and so it is very important to always test your blood sugar levels to see if any of your symptoms are related to either blood sugar level issues and treat accordingly.

What causes high blood sugar levels?

Many things can impact our blood sugar levels…


The biggest impact is food and drink and even with the other factors listed below, this is the single biggest thing that can have a huge impact.

Following a suitable diet which lowers and stabilises blood sugar levels is essential in managing the condition.

Take a look at our dietary advice on eating a suitable diet which may be different to what you are advised at the hospital.

typical ‘healthy’ foods and drinks are the most likely cause of high blood sugar levels


Being dehydrated can raise blood sugar levels. Take a look at our advice on what to drink and how often on our drinks page here.

drink water


When we are poorly, to help fight illness and get better our body releases extra glucose and with gestational diabetes, we cannot produce or use enough insulin to process this additional glucose. We have advice on colds and illness on this page and information on sickness with hyperemesis on this page.

Do not sit on high readings just because you are poorly. This excess glucose is still being passed through to your baby and so although this may be the reason contributing to higher readings, your blood sugar levels may need to be controlled with medication and/or insulin.


Not getting a good night’s sleep, or enough sleep can have an impact on blood sugar levels.


Stress and anxiety release hormones which raise blood sugar levels.


Steroids can raise blood sugar levels very high. If you are taking any medications which have steroids in them you should discuss this with your diabetes team.

If you are advised to have steroid injections to help mature your baby’s lungs, then many hospitals will admit you so that they can closely monitor blood sugar levels and use a sliding scale if levels reach too high. For more information on a sliding scale, please see this page.

Worsening insulin resistance and the need for medication

Gestational diabetes is a progressive condition meaning insulin resistance worsens the further into pregnancy you go. The sign of a good healthy GD pregnancy is increased insulin resistance and so don’t be surprised if your levels start to change and foods you once tolerated are starting to give you high numbers. Gestational diabetes typically shows between 24 – 28 weeks, but the hardest stage is between 32 – 36 weeks.

You should not feel like a failure if despite making dietary changes you cannot control your blood sugar levels. Please read more here.

Fasting blood sugar levels are extremely hard to control and there is very little we can do to impact these readings. For more information on high fasting levels, please read more here.

increasing insulin resistance in pregnancy

What are your test targets like?

It is important to follow the guidelines you are given by your healthcare professionals. In some hospitals, we have seen some very high post-meal targets being given (such as <10.0mmol/l after eating), or targets solely for pre-meals.

Bearing in mind that the NICE guidelines and most commonly used targets are <7.8mmol/l one hour after eating, you may want to discuss this with your diabetes team and ask for test levels which are in line with the NICE guidelines which are based on evidence-based research if you feel your targets are too high and could be detrimental to you managing and controlling your gestational diabetes.

For further information on testing blood sugar levels and current guidelines, plus our thoughts on additional testing, please see more here.