Does Night Testing Improve HBA1C?

Does Night Testing Improve HBA1C? Following a Hypoglycemia Event at Addenbrookes, I was on a mission to find out if exhausting night testing is really worth it and does it improve HBA1C results? Night testing is an emotive subject to parents of children with Type 1 Diabetes. This post is not intended to be judgmental in any way, it’s purely to understand the impact of night testing or more specifically night testing and correcting,  I do understand it’s not sustainable for so many parents. I have recently met a DSN that implied it was pointless to test/correct overnight when we were discussing ways to achieve the new Nice Guidelines on HBA1C results (6.5%).

My personal feelings as a night tester, was that my sons HBA1C would be much higher if I didn’t test and correct overnight, but I could be wrong. Also if I was right, that there is a direct correlation between working to control blood glucose levels overnight then CGMS really should be more freely available to children through the NHS, as frankly it’s down right exhausting at times without it.

So I set up a study with the help of parents within a couple of Facebook support groups. I was overwhelmed by the response, over 400 parents took part. A massive thank you to each and every one of you as the results are enlightening and have already changed my night time routine.


I set up a questionnaire  that included questions about overnight routines, to understand when people were testing, how often they were testing, what numbers they would correct overnight and what their latest HBA1C was.


Firstly here are the results of all those that took part in the survey, that had been diagnosed for more than 1 year. We will look later at the data of those that have only been diagnosed in the last year, later in the article.  I wanted to separate out the data to eliminate some of the effect due to the honeymoon period.

Action Taken Average HBA1C % Achieving 7.5% HBA1C Or Less % Achieving 7% HBA1C Or Less % Achieving 6.5% HBA1C Or Less
Never Night Test 8% Not Enough Data Not Enough Data Not Enough Data
Night Test Only When Ill or High/Low at Bedtime 7.98% 48.00% 25.00% 12.00%
Night Test Before Parents Bedtime 7.69% 50.00% 32.00% 9.00%
Routinely Night Test At Least Once 7.48% 60.00% 28.00% 14.00%
Routinely Night Test More Than Once 7.28% 71.00% 33.00% 16.00%
Users With CGMS 6.97% 78.00% 54.00% 34.00%

What does this table show us? There is a clear correlation between improved HBA1C and how often parents are Night Testing. However as we would expect the group using CGMS has the lowest HBA1C.  22% more children were achieving the old HBA1C Target of 7.5% when parents were routinely night testing more than once a night compared to those that only tested when the children were ill or had high/low blood glucose levels before bed which is currently the advice given by many hospitals and is probably one of the most sustainable ways to manage the condition from a quality of life perpective.  As I said before this is not designed to tell parents that they need to be night testing more often, it’s purely parent choice, and for many routinely night testing, particularly more than once, is not sustainable. There is nothing worse than exhaustion which can and does lead to Diabetes Burnout.

However I don’t think it can be denied that night testing is a way to improve HBA1C if you have energy or inclination. It also demonstrates just how effective CGMS can be when used properly. In my opinion the NHS and NICE really do need to start looking at this as an option to improve HBA1C results in children, currently only 18% of children in the UK are meeting the old NICE target of 7.5%. Using CGMS to alert a parent when a child is running high overnight would be very effective, also it would be more sustainable for parents to manage blood glucose levels overnight when they simply responded to alarms.


However, night testing is only half of the story. Many parents night test due to a fear of Hypoglycemia rather than to catch high blood glucose levels. If corrections are not done overnight then it’s unlikely the HBA1C will be reduced by night testing alone, in my opinion. Lets take a look at the effect on HBA1C when we analyse Correction Routines overnight.

This first table excludes CGMS Users in the survey, I have a separate table for those users further in the article.


Action Taken Average HBA1C % Acheiving 7.5% HBA1C Or Less % Achieving 7% HBA1C Or Less % achieving 6.5% HBA1C Or Less
Never Correct or Only Correct When Ketones are Present 7.66% 42% 25% 17%
Only Correct BG Levels Above 14 mmol 7.82% 53% 20% 8%
Routinely Correct BG Levels Above 10 mmol 7.05% 62% 36% 20%
Routinely Correct BG Levels Above 8 mmol 6.77% 82% 47% 22%

Now to me this is fascinating. You can clearly see that actively managing Blood Glucose levels overnight by correcting highs will reduce HBA1C Results.  Until now I have always corrected numbers above 10 mmol but it’s clear to me that I could potentially reduce my sons HBA1C by approx 0.25% if I routinely corrected numbers over 8 mmol instead. However I do think it’s a brave parent that will do this without CGMS and you would need to be confident with your correction factor.

Now let’s look to see if the same trends are shown in the group using CGMS. Here is the same table again but this time with the results from CGMS Users.

Action Taken Average HBA1C % Acheiving 7.5% HBA1C Or Less % Achieving 7% HBA1C Or Less % achieving 6.5% HBA1C Or Less
Using CGMS Correct Only Above 14 7.41% 54% 15% 8%
Using CGMS Correct Above 10 mmol 7.07% 67% 58% 33%
Using CGMS Correct Above 8 mmol 6.66% 87% 59% 43%

Once again the same trend is shown. The more aggressive you are with overnight management of blood glucose levels the better the HBA1C outcome.  In most cases the HBA1C is improved compared to those without CGMS also more children are hitting lower HBA1C levels with this technology.

Once again convincing me that one of the best ways hospitals could improve HBA1C results is to supply CGMS to those parents who would use it proactively to manage Blood Glucose overnight. If you do not respond to CGMS alarms to correct overnight you probably won’t achieve full potential.

I would like to take this opportunity again to thank everyone who contributed, I plan now to start correcting overnight for numbers above 8 in order to improve my sons HBA1C. I’m also going to look at funding a CGMS. You’ve all taught me something and I hope you have found this educational too, however how you choose to manage your child’s Type 1 Diabetes is personal choice.


Finally here are the results of the participants who have been diagnosed in the last year.

Action Taken Average HBA1C % Acheiving 7.5% HBA1C Or Less % Achieving 7% HBA1C Or Less % achieving 6.5% HBA1C Or Less
Never Night Test Not Enough Data Not Enough Data Not Enough Data Not Enough Data
Night Test Only When Ill or High/Low at Bedtime 7.47% 61% 30% 17%
Night Test Before Parents Bedtime 8.10% 71% 43% 14%
Routinely Night Test At Least Once 7.09% 76% 47% 35%
Routinely Night Test More Than Once 7.71% 37% 37% 25%
Users With CGMS 7.50% 65% 35% 29%

Here the results are slightly different.  The impact of CGMS on HBA1C is less obvious, though I think this could be due to it being used by more families that have a fear or Hypoglycemia, and I also think that is why the HBA1C is higher in those routinely night testing more than once.

However once again it appears that even in the first year of diagnosis, of those that routinely night test a larger percentage are achieving the lowest HBA1C’s.


Finally I did want to point out that in all groups there were some excellent HBA1C results regardless of night testing. Though I do think that the powers that be, do need to understand that night time blood glucose levels do contribute to HBA1C results and for many children the new targets will not be achievable under current guidelines from some hospitals, that night testing is not required. Also the introduction of CGMS to more children will make night time management more sustainable leading to better outcomes.

Whether you are a night tester or not I hope you’ve found this article about overnight testing and the effect on HBA1C interesting. I will say it again this is not meant to be judgmental it’s about providing information, from there it is parents choice. Quality of life is also important and understandably routine night testing just isn’t sustainable for many parents. I also wanted to highlight to those not living with this condition just how hard many parents have to work in order to achieve these tough targets.

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2 thoughts on “Does Night Testing Improve HBA1C?

  • February 1, 2016 at 4:52 pm

    Great article. We had clinic just last week (my daughter is almost 17, so heading towards transition) and during the part of the appointment when she was on her own with the consultant and dsn they mentioned there was a lot of night testing in her download, suggesting it was unnecessary. This shows otherwise. Kids are in bed for many hours (especially teenagers!), if we didn’t test and correct averages would definitely be higher. While they are still living at home parents just do whatever they can to keep them
    as healthy as possible.

  • February 18, 2016 at 2:00 pm

    Interesting, although entirely unsurprising. One thing I would add I don’t think a CGM necessarily gives you more sleep, just gives you the confidence to correct when you need to. For example last night I gave a correction at 1am and a correction at 4am. We probably got more sleep without it.

    I have literally no idea how anyone is supposed to manage diabetes without a CGM. It’s like being asked to control the temperature of an oven with no thermometer.


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