High fasting levels

High fasting levels or fasting hyperglycemia​1​, are a huge problem for many ladies. Fasting blood sugar levels (levels taken first thing in the morning when you wake up), are the hardest thing to control with gestational diabetes.  But why is that?

These were my BGLs in my 3rd GD pregnancy at only week 5 & 6 of pregnancy

When we’re sleeping we are not eating and drinking and we are not active and so the body is left to it’s own devices with regards to controlling blood sugar levels.

Impacts on fasting blood sugar levels

Many things can impact fasting levels:

  1. what you’ve eaten earlier in the evening
  2. when you last ate
  3. hydration levels
  4. how well you’ve slept
  5. the dawn phenomenon
  6. the Somogyi effect

What you ate earlier in the evening

Bearing in mind how much of each food group converts to glucose in the bloodstream and the time taken, your fasting levels may be impacted by this.

Too much carbohydrate in your evening meal or as a snack before bed can contribute to high fasting levels, as your body can only produce or use so much insulin, therefore if you raise your blood sugars too high by eating too much carbohydrate, your body can spend the night battling to try to lower your blood sugar levels.

A high fat meal such as takeaway food can also cause higher blood sugar levels and so eating a well-paired evening meal is important.

Macronutrients impact on blood glucose

When you last ate

The key to stabilising blood sugar levels is to eat small amounts, often. We obviously cannot do this throughout the night, but if you eat your evening meal early and do not eat again until breakfast the following day, it can be an extremely long time to go without eating. Likewise, if you eat a large meal just before going to bed, this too can have a detrimental effect on your fasting levels.

Hydration levels

Dehydration will cause higher blood sugar levels. Water helps to flush excess sugar from the body and so it is important to stay well hydrated.  Some ladies find it helps to take a big glass of water to bed with them so that they can also drink when waking to go to the bathroom in the night.

drink water

How well you’ve slept

Insufficient and poor sleep quality can lead to higher blood sugar levels​2​. Not easy when you are pregnant anyway and with gestational diabetes being linked to increased difficulties in poor sleep patterns​3​, but a good night’s sleep will help blood sugar levels, so ty to get a good night’s rest if you can!

Two more possible contributing factors to high fasting levels


Although lots of research publications for other types of diabetes, there is little research on the following two matters in gestational diabetes.  Although we know through the posts seen in our Facebook support group that fasting levels are a huge problem to mothers with gestational diabetes

The ‘Dawn Phenomenon

The dawn phenomenon occurs​4–6​ when the body releases hormones in the early hours of the morning (hence the ‘dawn’) in all people, diabetic and non-diabetic.  These hormones (including cortisol, glucagon, epinephrine and growth hormone) cause blood sugar levels to rise, giving the body a boost and wake up call to start the day.  This can typically happen anywhere between 3am and 8am.

In diabetics not enough insulin is produced, or insulin is not able to be used effectively in order to process this boost in glucose, resulting in high fasting levels.

Image credit: S Bhimji MD

Somogyi effect

Opposed by some professionals and researchers; a theory proposed in the 1930s by Dr. Michael Somogyi, Somogyi effect​7,8​ is also known as the ‘rebound hyperglycaemia’.  It only affects some diabetics, not all. When blood sugar levels drop low in the night (hypoglycaemia), the body responds by dumping glucose in order to raise blood sugar levels.

Image credit: S Bhimji MD

Possible ways to try to lower fasting levels

  • Go for a walk after your evening meal – exercise has a insulin type effect on the body’s cells which can impact many hours after and so may help lower fasting levels
  • Eat less carbohydrates in your evening meal – although remember that it is important to still eat sufficient carbohydrates to avoid ketosis, so carbs must not be completely cut from the meal
  • Drink plenty of water – take a glass of water to bed and have a drink when waking in the night
  • Eat a bedtime snack – eating a snack before bed has been the biggest success with ladies in our support group.  A snack which is high in protein and natural fat is believed to work best. Start with something like a couple of oatcakes and cheese, or a Ryvita with peanut butter. If this does not impact fasting levels, then try a high protein snack without the starchy carbohydrates
  • Apple cider vinegar – drink 2 tbsp apple cider vinegar at bedtime with 1 oz (a thumb size piece) of cheese. A small study​9​ in type 2 diabetic patients found that drinking 2 tbsp of apple cider vinegar and eating 1 oz cheese lowered fasting levels by 4% (and up to 6% in some patients)

Some ladies with gestational diabetes have had great success with apple cider vinegar and so it’s worth trying if you have the stomach for it!

Please note: As vinegar is acidic, it is advisable to dilute it in some water and brush teeth after consuming

apple cider vinegar

There is no evidenced-based research to suggest that the apple cider vinegar should contain ‘the mother’ (where the apple cider vinegar is cloudy due to being unrefined and unfiltered) to be beneficial to blood sugar levels and it does not need to be pasteurised due to the high acidic content limiting bacterial growth.

I’ve tried a bedtime snack and it’s not working?

We often get ladies in our support group saying “I’ve tried a bedtime but it doesn’t work for me”, yet when asking what they’ve tried they’ve had fruit or toast etc.

The best things to eat are high protein and high natural fat

nuts, seeds, peanut butter
high protein and natural fat works best as a bedtime snack. Nuts are an ideal source

Bedtime snacks may take some playing around with to find what works best for you. As your pregnancy progresses and your insulin resistance increases, you may need to change to find things that work better.

A bedtime snack does not work for everybody.

Depending on what is eaten, some ladies see higher fasting levels from eating bedtime snacks, but many that have eaten bedtime snacks have had good success.

Please note: It is very common to be advised not to eat after a certain time of day by your dietician or diabetic team. This causes some huge problems for shift workers, night workers, or those that eat late in the evening.  Our advice of eating little and often may be opposed by the advice given to you by your diabetes team.  Only you can be the judge of this and see what works best for you personally, but eating little and often (no matter the time) and having bedtime snacks has been successful for the majority of our support group members.

myo-Inositol Supplementation

Inositol, also known as vitamin B8, is a naturally occurring product found in a variety of foods. The body also produces its own inositol.

There are 9 different types of inositol. Myo-inositol can be found in cereals, corn, green vegetables and meat. It can also be taken as a supplement in powder or tablet form.

Myo-inositol plays a part in many of the body’s functions, one being sensitivity to insulin.

A few studies have found that taking this supplement during pregnancy had beneficial impacts on blood glucose levels.

A meta-analysis​10​ published on the Cochrane Database of Systematic Reviews of two studies (142 women) in Italy, reported that taking 4g myo-inositol daily, plus 400μg folic acid daily, was associated with a reduced change in maternal BMI and fasting blood sugar concentration compared with a placebo.


myo-Inositol safety in pregnancy

There have been many studies in the use of myo-inositol supplementation in pregnancy with studies showing that the supplementation of 2g twice daily may reduce the incidence of gestational diabetes​11​ and have some other beneficial outcomes, such as reduced rates of neonatal hypoglycaemia​12​.

However, as these are still small studies, with the supplement still being in it’s trial stages​13​, myo-inositol is not currently classed as safe for use in pregnancy.

You should always consult your diabetic medical professional team before introducing this supplement to discuss whether it would be suitable for you to take

You can only do so much!

High fasting levels are typically less responsive to diet or lifestyle changes meaning many women who struggle will need the additional support of Metformin and/or insulin and that’s OK!

Medication and insulin

High fasting levels are very common with gestational diabetes and are the hardest level to control.

For the majority struggling with high fasting levels, the only way to improve them is with the help of medication such as Metformin and/or insulin.

By being prescribed medication and insulin to control your blood sugar levels, you should not feel you have failed (something we often see ladies saying in our Facebook support group).  For many, it is the only way to achieve good fasting levels when all other methods above have been tried.

Medication or insulin may not work immediately

Many ladies are confused to see higher or even worse levels the morning after starting medication and/or insulin.

Metformin and insulin cannot cause higher blood sugar levels. However, stress or concern over starting meds, alongside rapidly increasing insulin resistance may mean it takes a little while, or increased doses before the benefit is seen

Medication such as Metformin, can take a while to build up in your system before you see an improvement in blood sugar levels and doses may need to be increased before sufficient impact is made.

Slow release insulin will start working immediately (releasing slowly through the night and up-to 24hrs from the time of injecting), BUT it may take a while to get the dose right and doses may need continually increased until the benefit is seen on a daily basis. Insulin doses are started low to prevent hypos and are titrated as needed until the benefit is seen.

Bedtime snacks used alongside medication/insulin have helped many ladies keep doses lower for longer and so you may want to try snacking even if you are being medicated for fasting levels.

It’s typical that insulin doses will have to be titrated as the pregnancy progresses. It’s important to work closely with your diabetes team to ensure you increase doses as necessary. Please do not sit and wait for your team to call you, or for your next appointment if you are experiencing high fasting levels. After 3 or more high fasting levels, give your team a call to discuss insulin doses.

If you have been advised to increase your doses yourself in small amounts and are still struggling with high levels, go back to our team to suggest making a slightly larger increase in order to get the levels under better control.

high fasting levels written in blood glucose monitoring diary

Why are fasting levels important?

Fasting levels give an indicator of our baseline blood sugar levels. This shows an picture of what our levels are returning to when they are not complicated by the foods we are eating.

High fasting levels have been associated with increased adverse pregnancy outcomes [large for gestational age babies, hypertensive disorders of pregnancy, preterm delivery, composite adverse outcomes (shoulder dystocia, erbs palsy, or clavicle fracture), c‐section, induction of labour, NICU admission] in many research studies​14–16​

A large Canadian study published in Nov 2019​15​ of 257,547 pregnancies between 2008 -2014 found that those diagnosed with high fasting blood sugar levels (over 5.3mmol/L) following the GTT resulted in the highest rates of adverse pregnancy outcomes (more so than those diagnosed with high 1hr or 2hrs post glucose levels) .

elevated FPG was significantly associated with a higher risk of LGA and HDP outcomes compared to post‐load elevation in GDM pregnancies. We also found that the use of pharmacological treatment (predominantly insulin) was highest in pregnancies with elevated FPG and treatment rates increased with increasing dysglycaemia (one, two or three elevated values on the OGTT). After adjusting for other maternal factors, FPG was associated with an increased risk of LGA and HDP outcomes in GDM pregnancies with and without pharmacological intervention.

Elevated fasting plasma glucose in women with gestational diabetes is a stronger predictor of large‐for‐gestational‐age and hypertensive disorders of pregnancy outcomes than elevated post‐load glucose

Elevated fasting vs post‐load glucose levels and pregnancy outcomes in gestational diabetes: a population‐based study

Higher fasting levels in the first trimester has been linked to increased risks of adverse pregnancy outcomes​17,18​

Higher first-trimester fasting glucose levels, within what is currently considered a nondiabetic range, increase the risk of adverse pregnancy outcomes. Early detection and treatment of women at high risk for these complications might improve pregnancy outcome.

First-Trimester Fasting Hyperglycemia and Adverse Pregnancy Outcomes

Some women may struggle with high fasting levels, yet post meal levels stay well controlled and vice versa. For others that are more insulin resistant, they may struggle with both high fasting and high post meal levels.

Both high fasting and high post meal levels should be lowered and controlled to help minimise complications caused by gestational diabetes.

Future risks post birth

A 2002 publication​19​ from Diabetes Care comparing 28 studies found that elevated fasting levels during pregnancy was the most common risk factor associated with future risk of type 2 diabetes:

Cumulative incidence of type 2 diabetes increased markedly in the first 5 years after delivery and appeared to plateau after 10 years. An elevated fasting glucose level during pregnancy was the risk factor most commonly associated with future risk of type 2 diabetes.

Gestational Diabetes and the Incidence of Type 2 Diabetes


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