Tuesday 19 March 2019

I like driving in my car: glucose monitoring at the wheel.

"I like driving in my car”, sang Madness back in 1982. And for better or worse, many of us do: it may be potentially dangerous, expensive, selfish and environmentally harmful, but driving is one of the pleasures of adult life in the modern world. Passing the driving test is one of the great rites of passage of life for those of us fortunate enough to have the means to do so, and in contemporary society, the private car has given us access to choices in our working lives and leisure time that were unimaginable only two generations ago.

So the ability to drive, safely, affordably and comfortably, is something which we cherish, and any loss of the ability to do so is hard to bear. As the Royal Family recently experienced, convincing an older person whose faculties and judgement are past their best, that the time has come to give up their car and their licence is a difficult business. And for those of us who live with a medical condition which might impair our ability to drive a car, the thought of losing our freedom to drive is a painful prospect.

Thankfully, for many of us living with Type One Diabetes and treated with insulin, that prospect is one which, with good management of our condition and a bit of luck, we can avoid. Yes, we have to renew our licence every 3 years, and in so doing we have to re-confirm our fitness to drive and authorise the DVLA to check that fitness with our doctors, but for the most part, we get our new licence and drive like everyone else.

However, it’s not like everyone else, because we - quite rightly - have to undertake to check our fitness to drive on each and every occasion we get behind the wheel. In many ways, this is no big deal, given the fact that people with Type One are constantly monitoring their fitness to do anything, all day and every day.

But it’s the means by which we can carry out that monitoring which has, until recently, been one of the most burdensome aspects of living with diabetes. An accurate finger prick test requires our full attention, a washed pair of hands, the use of both hands, somewhere to dispose of a test strip contaminated with blood and a tissue to clean up afterwards. Self-evidently, this is not possible whilst driving, so people with Type One have to stop the car in order to test, as well as testing before every journey. I suspect that many of us do what I always do, erring on the side of higher glucose levels for a journey of any length - a strategy which, if repeated regularly brings its own risks of insidious long-term damage and potential complications.

So the recent decision by the DVLA to accept the use of CGMs and Flash monitors for testing our fitness to drive has been a most welcome development and a victory for common sense. Click here for a PDF of these latest, updated, guidelines.

It is clear that the information provided by CGM or Flash is not just sufficiently accurate to be regarded as a safe proof of fitness to drive but is actually far better than the snapshot figure provided by a finger prick test. Back in 2017, I produced a short report for the APPG for diabetes on this topic, showing how a Libre result with its trend arrow was infinitely more helpful - not to say safer - than a finger prick test result. This was presented to the DVLA as part of their deliberations, so I like to believe that I played my own small part in bringing about this decision.

Click here to see this document.

But what about testing whilst driving? This is a grey area, although this section in the DVLA guidelines appears to state that we are not allowed to do so:

"If you are using a glucose monitoring system (RT-CGM or FGM) you must not actively use this whilst driving your vehicle. You must pull over in a safe location before checking your device. You must stay in full control of your vehicle at all times. The police can stop you if they think you’re not in control because you’re distracted and you can be prosecuted."

I think this merits further thought and potentially some guidance and clarification. As things stand, the change in the DVLA rules speaks of CGM or Flash as an alternative to finger prick testing before driving, and every two hours thereafter to ensure that blood sugar levels are safe and stable. However, given the ease of using CGM or Flash, is it not safe, or indeed desirable, to test whilst driving? Here, we stray into more complex territory, that of driving with due care and attention. Is it safe to use and read a monitor whilst driving? And for that matter, is it legal? 

Let’s deal with the legal first: I am ready to stand corrected, but as I see it, the legality of using a CGM of Flash reader whilst driving is less than clear, with a very important caveat: the use of the mobile LibreLink App, or any other diabetes tech which uses a mobile phone, is clearly illegal as far as I can see. The law has expressly forbidden the use of any handheld communication device whilst driving, so the use of a phone for LibreLink or similar would be illegal in the same way that it is illegal to us a phone’s satnav function. See this page from the CPS which gives good guidance on the legal definitions of handheld communication devices, and as far as I can see makes clear that using a smartphone app to check blood glucose is illegal.

But of course, the FreeStyleLibre reader is not a communication device and so is it is not technically illegal to he holding one whilst driving. But is it safe? 

Well in my view, yes. I now keep my Libre reader on the dashboard (on one of those non-slip mats), where it is within easy reach and I feel that to turn it on, swipe and read is safe and helpful, provided that the driver chooses a suitable moment and road situation: stopped at lights, driving along a quiet, straight road etc. It is no different to, and subject to the same common sense rules as, changing radio station, adjusting the heating or even eating a travel sweet (my pot of jelly babies is always to hand whilst driving).

My Libre Sensor on the dashboard
Moreover, and indeed more safely, someone else can take a reading. With a Libre sensor on the driver's left arm, a passenger in the front seat can easily swipe and check, and I have already asked my wife and daughter to do so for me with me at the wheel.

Am I right in extolling the virtues of occasional checking whilst driving? I hope so, and certainly, in my own mind, I am significantly safer now than when following the previous regulations requiring a finger-prick test every two hours: I suspect that I was far from alone in being somewhat liberal in my interpretation of that rule. We all know that a lot can happen to blood sugar in two hours, and the idea of driving for two hours without knowing the current BG level, let alone the direction of its travel, seems now to be rather foolhardy, and the ability to keep tabs on that level, even whilst at the wheel, seems to me to be a very positive and beneficial development.

My thanks to FreeStyle Libre campaigner Nick Cahm for giving a second opinion on this piece: his post here was the original stimulus for my writing this post and is well worth a read.

Disclaimer: This post, like all else that I write, represents my personal views and experiences. I have no medical or legal qualifications or expertise, and all people with diabetes who drive should ensure that they drive safely and legally at all times.


  1. Hi Adrian,

    This is eminently sensible and practical advice :)

    It's absolutely brilliant that the DVLA now include CGMs in the guidance.

    I usually find my blood sugar climbing up on long car journeys too, with the lack of activity and inevitable snacking at service stations! It’s often really hard to find food on-the-go that’s diabetic friendly :(

    The background low alarm on the forthcoming Libre 2 will greatly enhance driving safety.

    I appreciate that I'm very fortunate to be able to self-fund the Dexcom G6 which also has a predictive low alarm. It synchronises well with the Apple Watch and it’s easy to glance at the BGs with hands on-the-wheel. But I really empathise with Nick Cahm’s comments about the huge disparity in self-management education and availability of technology across the T1DM population as a whole in the UK.

    For motivated patients, CGMs (in synergy with smartphone Apps) have the potential to be a real life changer, but are only valuable with the appropriate education and support in place to make the most of them. It’s fantastic that the ABCD Freestyle Libre webcast tonight is already oversubscribed :)

    Thank you again for all your time with the wonderful blog :)

    With best wishes,


  2. Many thanks as always, Ian, for your supportive, appreciative and constructive comments.

    Your responses are greatly valued.

    With every good wish,


  3. I have added and shared your site to my social media accounts to send people back to your site because I am sure they will find it extremely helpful too. Road Test


Go Your Own Way

  I developed Type One Diabetes just over 26 years ago, in December 1997. I have often said that it was a good moment to join that “club tha...