What Difference Does Training In The Morning VS The Night Make To Blood Sugar Levels?

As I'm away on holiday at the moment and as it's getting dark early with these winter nights, some of my training sessions have been in the morning opposed to my usual time of training in the night. At least once a week normally, I train on a Sunday morning, at the sand dunes doing sprints or on the track doing block starts. But the rest of my training is conducted in the night. Having had diabetes for over 13 years I know all too well that diabetes loves routine and in relation to that, if you can pick up patterns in your diabetes results then it can be of great benefit the management of the condition. But identifying the affect of training in the morning opposed to in the night was a pattern that took a little longer to identify, so I think it's really important for me to share my findings with you regarding this quite complex diabetes and training problem.

As I briefly mentioned in my introduction, the greater majority of my training sessions are done in the night at about 7pm. When I train in the night I have healthy snacks, lunch and breakfast before training during the day. But I choose to have tea after I've finished training, opposed to before because I find it helps me better recover, avoid night hypos and not want to throw it back up when eaten before the session. After night time track training no matter the type whether sprinting/ speed/ endurance/ circuits my blood sugars are between 7.0mmol and 12.0mmol in the hour that follows.

However, when training in the morning I was noticing that my muscles hurt a lot more after training, my blood sugars would be in the teens until lunch time (training starts at 9am) and beyond. Doing things like changing my set, and correction dose injections didn't seem to help this spike in my blood sugars. I can understand that reading this, your first thought would be that it must be the adrenaline causing the blood sugar spike. But call it intuition I just knew that this was not the cause of the high blood sugars. I conducted ketone tests for the blood sugars that were 14.0mmol and over, especially because my muscles were aching the way they do when I have ketones. What I found was that my ketone levels would rise from their normal 0.0 to up to 0.4 sometimes even 0.6, at which point I sought medical advice because as I mentioned, correction doses weren't working effectively.

It was when Sunday sand dune sessions stopped and became blocks sessions that the penny finally dropped as to what was going on. As I would do a blocks session on a Wednesday night as well and had done so for the last 8 weeks, I knew that this session did not cause an adrenaline spike for my blood sugars and this included when I was trialling the libre sensor and could see precisely what was happening. But then when it came to doing the same session in the morning, my blood sugars were going high post exercise and my ketone levels were elevated for a couple of hours after too. One clue to what I believe was happening, was that overnight I have a very minimal need of insulin to keep my blood sugars in range of 0.450IU from midnight and 0.750IU from 4am and these are the precise amounts I need. There's also a consideration that when people with diabetes are waking up, they experience an affect named the 'dawn phenomenon' which is a period of time in the early hours of the morning when insulin requirements by the body rise and more insulin is needed so as not to go high.

The other thing I should mention about training in the morning is that because my 'wake-up' and 'pre-breakfast' blood sugars after often in single figures, between 6.0mmol and 8.0mmol, this is lower than I would like to start a 2 hour training session. So I put a temporary basal on, which for those who don't pump is when you reduce your hourly background rate of insulin by a percentage. And I think it was this that was causing the spike later on in the morning- that my insulin requirements in the morning and my lower 'insulin on board' compared to the night meant I couldn't afford to reduce my background insulin rates for sport in the morning as it resulted in highs. What I did to resolve this problem was continue to have a good breakfast of carbohydrates before morning training, test regularly, not put down my background rate of insulin and keep jelly babies to hand for between runs to ensure that lows didn't happen during the session and so far it's worked really well.


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My blog takes you through a daily look at sport, diabetes and everything in between. As an athlete that lives with type 1 diabetes I want to let you into news, views and all that is important to both of my passions.

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