Thresholds for diagnosing gestational diabetes
Hospitals do not have to use the recommendations listed below and so different targets for diagnosis are used all over the UK & Ireland. As a result, all this can cause a lot of confusion!
Diagnosis test target levels England & Wales:
Diagnose gestational diabetes if the woman has either:
- a fasting plasma glucose level of 5.6 mmol/litre or above or
- a 2‑hour plasma glucose level of 7.8 mmol/litre or above. [new 2015]
Diagnosis test target levels Scotland:
- The adoption of internationally agreed criteria for gestational diabetes using 75 g OGTT is recommended: fasting venous plasma glucose ≥5.1 mmol/l, or one hour value ≥10 mmol/l, or two hours after OGTT ≥8.5 mmol/l.
- Women with frank diabetes by non-pregnant criteria (fasting venous glucose ≥7 mmol/l, two hour ≥11.1 mmol/l) should be managed within a multidisciplinary clinic as they may have type 1 or type 2 diabetes and be at risk of pregnancy outcomes similar to those of women with pre-gestational diabetes.
Diagnosis test target levels Ireland:
A diagnosis of gestational diabetes is made when one or more values are met or exceeded
- Fasting 5.1mmol/L
- 1 hour 10.0mmol/L
- 2 hour 8.5mmol/L
Borderline diagnosis can have very different meanings when it comes to gestational diabetes. It could mean that following your GTT your fasting or post glucose levels were:
- Just below the threshold targets
- Bang on the threshold targets
- Just over the threshold targets
Bearing in mind that test threshold levels differ from one hospital to another, this could be a huge difference in actual blood glucose levels and therefore what is classed as a borderline diagnosis in one hospital may be a clear positive diagnosis result in another.
Our point of view is that if you have been told to monitor your blood glucose levels, then you are being monitored for gestational diabetes and should modify your diet to a GD friendly one. It is also very common for borderline diagnosed gestational diabetics to have increased insulin resistance further into the pregnancy, resulting in medication and/or insulin being used to help control levels. Therefore, borderline diagnosed ladies are at no less risk than those that are 'just diagnosed' with a positive result.
Problems caused by borderline diagnosis
One of the biggest problems caused by ladies being told they are 'borderline', is that many ladies then believe they have been misdiagnosed, do not have gestational diabetes or do not have it 'that bad'. Many believe they do not need to follow a different diet and that they certainly would not need medication or insulin at any point.
Through research conducted in our Facebook support group, we can safely say that borderline or not, it's best to follow a good diet which will help control blood sugar levels, alongside exercise. You will see from the many comments below, many ladies still needed help with medication or insulin to keep blood glucose levels under control, even if they were told they were 'borderline'
Our research regarding borderline diagnosis of gestational diabetes:-
- I was told I was borderline, I was fine for the fasting test and 0.1 over for the after the glucose test. I was originally diet controlled, but despite trying my hardest with the diet my hormones took over and about 4 weeks after finding out about GD I was put on metformin. By the end of my pregnancy I was on 2 metformin with breakfast and 2 metformin with tea xx
- I was 5.7 for fasting (.2 over) and fine after. Midwife dismissed it and said retest 6 wks after baby. Only referred me as I had sugar in my urine (only time). Took over 1 month to see diabetic midwife as I was low priority. I was on insulin 3 days after testing and never got my fasting levels within range xx
- I was told they had just changed the threshold and was just over the new threshold "borderline". So if I'd gotten tested a week before I wouldn't have been diagnosed with it. Ended up on metformin.
- I was only just over too, diet control for just over a week then metformin for a few weeks and metformin and insulin for the rest of pregnancy. Numbers just kept rising even though I was careful with what I ate x
- They originally told me I had 'just' failed the test, I never ever took it as that and right enough my GD developed badly and I was on metformin and glebenclamide to control my numbers and still could only eat little to no carbs xx
- I was borderline too and ended up on max metformin x
- I was below the target set for 2 hours after the drink. Was diagnosed based on a high fasting reading. Very quickly needed Metformin and then insulin x
- Was just told I was over, it steadily got worse even when I was taking metformin and diet controlled, they then put me on insulin
- My 2 hr was 7.8 which had to be under 7.8 to pass, fasting was fine. In 4 weeks I was 2x500mg metformin twice a day and 28 units of insulin at night, plus had to have the odd 2 units of rapid insulin too
- I was on the line for post - 7.8 - put straight onto metformin but ended up on insulin at 35weeks, but pre test I'd had a bad headache for 2 weeks & craving sweet stuff. Changed to GD diet, joined group & found body much happier. Post pregnancy ggt had good numbers
- I was technically "borderline" as 0.1 over for my fasting. Ended up on 4 metformin a day x I'm sure the threshold was 5.3 and I got 5.4
- I was 0.1 over the fasting, and remained diet controlled x
- They said I was borderline as soon as I was diagnosed with Gd they put me on metformin
- Fasting was 4.6 and 2 hours after was 7.9. I stayed diet control xx
- I was 2 marks above 'normal'. Started off diet controlled then ended up on metformin and insulin X
- I had to be under 7.8 but my GTT was 7.9 I was diet controlled for 10 weeks until my little lady arrived!! xx
- I was told borderline, think the cut off was something like 7.7 and I was 7.8. I was diet controlled but changed what I ate and really stuck to it and just had a controlled treat on a Friday xx
- I was told borderline cut off was 5.1 fasting and 7.8 after, my gtt results at 28 weeks were 5.1 and 6.3, I was diet controlled an luckily never ever got higher reading than a 9 but that was occasional, it was generally no higher than 7.8, my baby was 8lb 11 born an her sugars were ok. I hate 'borderline' it's so confusing surely you either have it or you don't??! Xx
- Don't have my results to hand but I too was told I was borderline. I think this must be some misguided attempt to stop people from panicking but in reality, in my case anyway, being told I 'only just' failed the test added extra confusion to an already confusing condition. For example, it caused a lot of anxiety when they wanted to medicate me straight away, because all I knew about metformin at the time was that it crossed the placenta...which sounds really alarming when you've not had a chance to do all your homework yet, and I couldn't get my head around why they would take that course of action if results were so borderline. I was so confused and terrified that first week because I was getting a lot of mixed messages from my consultant and DMW, so it was more of a hindrance than a help to be told I was borderline. Its really irresponsible as they know tolerance levels can change rapidly. Mine did and within a couple of weeks I needed insulin four times a day. x
- I don't remember the exact numbers but the consultant told me I was 'borderline' - within the same NHS trust but two hospitals apart they use different targets and I wouldn't have been treated as gd had I been going to give birth at the other hospital! Having said that I ended up on both insulin and metformin. Believe me, I took the diagnosis very seriously and stuck to the diet as much as possible!
- 0.1 over the 2hr blood test at 27 weeks (I was 7.8 the cut off here is 7.7), four days later I started testing and got an 11.0 2hrs after a bowl of homemade vegetable soup! I was sure the diagnosis was wrong as well! 1 weeks diet controlled, had to cut out all carbs and lost 7lb. 1 weeks on 2 x metformin, another week on 4 x metformin. At 3 weeks after diagnosis I also started insulin for fasting and for breakfast, 4 units each. Fast forward to 38 weeks and I was on insulin for all meals (30+ units for breakfast, 15-25 units @ lunch and dinner depending on what I ate - got quite good at working that out ) and 80+ units for fasting. The only fasting reading I had in range (below 6) was the morning of my section when I got a 5.8. At the end I was upping the night time insulin by 4-8 units each night just to keep the numbers from increasing, they certainly didn't want to go down. I also passed the postpartum GTT with a 5.6 fasting and 5.7 after two hours x
- I was .2 over on my 2hr post bloods, was on 4 x Metformin a day and 28 units of Insulin by the end xx
- I don't remember my fasting number but after 2 hours it was 9.1 - the Dr said I was borderline at 9.1?!
- Mine was 0.2 or 0.3 over the target. I was on metformin. I definitely had GD as I really felt the effects of highs or lows and had to cut a lot out of my diet to keep my numbers just in tolerance
- I was 0.6 over and diet controlled
- I was borderline (they used another word but can't remember what it was!) 0.1 over. I was diet controlled for 3 weeks then on metformin (ended up on max dose) XX
- I was .1 on the over on my first gd pregancy. Diet controlled and baby induced at 39 weeks due to placenta failure secondary to the gd. On 2nd pregnancy I was over by more (can't remember the numbers). Again diet controlled and on issues with placenta.
- I was only just over and I stayed diet controlled
- I was .1 over and diet controlled
- was 0.1 over (5.6 fasting) and was metformin and insulin controlled x
- My hospital 1hour post cut off is 10.1!!!, I was 9.3 at 24 weeks, hospital test & 10.2 at 28 weeks GP test
- I was way over... 11.4 and got told I would be on insulin pretty quickly... But stayed diet controlled the remaining 12 weeks. Just shows its unpredictable and just because your loads over doesn't mean anything and nor does borderline!
As it is, are NICE guidelines for diagnosing gestational diabetes too high?
Cambridge University research article - New NICE thresholds could miss up to 4,000 women per year at risk from diabetes in pregnancy
This review found interventions including providing dietary advice and blood glucose level monitoring for women with pregnancy hyperglycaemia not meeting GDM and T2DM diagnostic criteria helped reduce the number of macrosomic and LGA babies without increasing caesarean section and operative vaginal birth rates. It is important to notice that the results of this review were based on four small randomised trials with moderate to high risk of bias without follow-up outcomes for both women and their babies.