Caution: Nothing in this blog is medical advice. Diabetes is highly individual. Always consult your healthcare team before making changes to your exercise or insulin routine.

Here's something that sounds wrong but isn't: a 15-minute impromptu walk to the shops is harder for me to manage than a 2-hour run.

The reason is simple. Diabetes is really hard to deal with in impromptu situations - a quick blast of energy you weren't expecting, with no preparation and no food on you.

I'm not saying a 2-hour run is easy. I'm saying that when I go on a 2-hour run, I'm planning for it. I disconnect my pump. I have two or three gels in my pockets in case of a low. It's not that it's easier - it's that I've planned for it. And that's one of the key things about exercise with diabetes: it's not intensity or duration that makes it hard to manage. It's predictability.

The Gap Between Theory and Reality

When you get diagnosed, you get a lot of theory about how exercise and diabetes interact. Aerobic exercise tends to lower blood glucose. Anaerobic exercise like weightlifting and sprinting tends to increase it. But apart from that, there isn't really a lot you can take from it. And the fact of the matter is, you might respond differently. There are general patterns, but the nuance is very specific to you.

For example, I've never used the exercise mode on an insulin pump. In fact, I've never worn a pump while exercising. Unless I'm out for two, maybe three hours, I have no need for insulin during exercise - I just don't need it. Pumps have all these features, exercise modes and algorithms, but I've never found them useful. Disconnecting is what works for me. I think most people would find that surprising, but it's just what I've landed on through years of trial and error.

Another thing: I know my body's routine for the best time of day to exercise. If I exercise in the morning, fasted, I have a very low likelihood of going low. It's just super stable at that time. I genuinely don't know why -I'm sure there's a physiological explanation involving cortisol and dawn phenomenon, but honestly, I just know it from doing it hundreds of times. Whereas in the afternoon, post-lunch? That's a danger zone. You have a high level of insulin circulating, and exercise supercharges its effect.

The key thing is: none of this came from a textbook. It came from doing it, getting it wrong, and doing it again.

Exercise Isn't Just Important - It's Foundational

I've got to a point where exercise is such a big part of my routine that it's the norm. I exercise pretty much every day. And when I can't - through illness, injury, or just life getting in the way - the difference is stark.

My insulin needs go up by 25-30%. That's not a marginal difference - that's a fundamental shift in how my body processes insulin. My postprandial blood glucose is much higher. My insulin sensitivity drops. Everything becomes more difficult. And if I continue not exercising, the needs keep increasing. Within days, the whole system shifts.

When people talk about exercise being important for diabetes, I don't just see it as important. I see it as one of the fundamental treatment cornerstones of this condition. My control isn't perfect - far from it - but it would be a hell of a lot worse without exercise.

You Will Get Things Wrong

If you've had this condition for a few years, you're trying to exercise, and you've crashed low during a run or spiked to 18 mmol/L after a gym session - I completely empathise with your situation.

This is really, really hard. And the hardest part isn't the physiology. It's that when the numbers don't add up, it feels like you're failing. It feels like you're doing something wrong. It's very easy to spiral into negative self-talk, to replay what you could have done differently. I've been there plenty of times myself, even after 30 years.

But it's never helpful to think about it that way. It is what it is. It sometimes works out, and sometimes it doesn't.

The thing I'd say is this: take the learnings that are being presented to you. There is a lesson in every bad reading. But steer away from self-judgement and instead focus on what you can try differently. You have data. It's a signal. You can use it to refine your approach.

That doesn't mean things are going to be perfect. But I don't know anyone who has mastered this who hasn't somewhat failed their way to success. It's really difficult, and I wish it wasn't.

Start Small. Track Everything. Keep Calibrating.

If you want to get into exercise - maybe you've had the condition for years and completely stopped, or maybe you've never really started - my advice is simple: start small.

This is not about an overnight transformation. It's about incrementally adding exercise into your routine until it becomes part of your routine. Diabetes thrives on consistency, so you don't want to go from zero to 100 in one week. Everything will go haywire, and you'll lose confidence. This might sound obvious, but I think a lot of people underestimate how much the body needs time to recalibrate.

Start with walks if that's where you are. Pay attention to what happens before, during, and after. Your insulin and your sugars will need adjusting as you go - that's normal and expected.

As you start to do more, you'll accrue more signal about what's happening. And I want to be clear: this is a constant calibration. It's not a one-time thing where you figure it out and then you're done. Insulin sensitivity adjusts as exercise load does. It's also affected by stress, sleep, illness, and a dozen other things.

But you can certainly build a track record of what happened before - what time of day, what duration, how much insulin on board, what was the outcome. It's not a perfect predictor, but it's an incredibly useful indicator.

That's exactly why I built Glucose Insights: to help you look at different activities, filter by time of day, see glucose before, during, and after, and start spotting the patterns that would otherwise take years to notice intuitively.

No one can hand you a perfect playbook for this. The playbook is yours to write. But the more you track, the more you experiment, and the more you treat setbacks as data rather than failures - the faster that playbook comes together.

It won't be perfect. Mine certainly isn't. But it'll be yours, and that's what matters.