“Diabetes is a numbers game” – A guest blog by Andy Broomhead

Living with diabetes puts your mathematical skills to the test every single day.

It involves a lot of numbers and mental maths to ensure that your body is getting the right amount of insulin.

In Andy’s latest post, he explains the numbers involved in type 1 diabetes in an easy to understand way so you can best manage your own diabetes…


Fine margins

The things I go on about above all else when talking about diabetes are that it’s a numbers game, and the margins associated with those numbers are incredibly fine.

My go-to analogy for this kind of thing is tightrope walking – you might be able to keep your balance, but a wobble one way or the other is a potential catastrophe.

I was recently pondering just exactly how fine these margins are.  How much of a wobble is needed before we’ve lost our balance?

Whilst day-to-day diabetes involves a lot of numbers and mental maths, we’re all individual and so what you need might be fundamentally different to my requirements.

To illustrate how fine a line we walk, I’ll use the numbers from my daily diabetes journey (and a couple of assumptions along the way)…


The numbers

My pump’s correction range is 5.5mmol/L to 6.5mmo/L – so whenever I use the Bolus Wizard, it’ll calculate any adjustments trying to get me back into that range.

• I need 1 unit (1u) of insulin to cover every 10g of carbohydrate I eat.

My insulin sensitivity factor is 2.8 – that is, I expect 1u of insulin to reduce my blood glucose (BG) by 2.8mmol/L. If I had a reading of 9mmol/L on my meter and took 1u of insulin, I’d expect it to alter my glucose to 6.2mmol/L.

I feel confident in all of that information, having road tested it every day for 14 years.

Finally, we need to make an assumption.  The SI unit for a drop of water (which we’ll assume to be the same as a single drop of insulin) equates to 0.050ml

10ml vial of fast acting insulin

A standard 10ml vial of fast acting insulin


Now for the maths

A standard 10ml vial of (standard strength) insulin contains 1000 units of insulin (which would be some serious carbs by the way).

So let’s get that down into something more manageable…


Millilitres Units
10 1000
5 500
1 100
0.5 50
0.05 5


Hopefully, that last line is now familiar.  Five units (roughly) equates to a single drop of insulin.

Going back to the earlier discussion of insulin sensitivity, in order to lower my blood glucose by around 3mmol/L, I need one-fifth of a drop of insulin. One. Fifth. Of a single drop.

That’s a fine margin indeed, and no wonder that insulin is one of the most expensive liquids on the planet.  (At this point, I’m once again thankful for the NHS here in the UK).

I think the margins involved in raising blood glucose are probably a lot more familiar to us as people living with type 1.

Lifting ourselves from a delicate 3.5mmol/L requires about 15g of (fast acting) carbohydrate.   If we can hold our nerve (and resist the call of the biscuit tin) for the advised 15 minutes, we should be back in a more comfortable range (roughly 6.5mmol/L).

I think dealing with hypos means many of us can estimate 12-15g or carbs quite easily (3 or 4 GlucoTabs, about 5 Jelly Babies, 150ml of fruit juice…. 1 chocolate Hobnob…) and because we’re accustomed to thinking in those terms it becomes part of our daily life.

insulin drop

A single drop – more than enough to cover a few biscuits

Understanding the numbers involved in treating higher blood glucose readings really brings home how thin a line we tread.

Not quite counting our carbs properly is one thing, but the knock on difference when delivering such small quantities of insulin is enormous.

Next time you’re dialling up a correction dose to bring yourself back in range, don’t be hard on yourself.

Chances are you were less than a drop of insulin out in your calculations – you’re doing a great job!

Let us know in the comments box on how you deal with the daily maths of diabetes and also go check out Andy’s previous blog on illness and diabetes for guidance on when you’re not feeling your best! 

You can find Andy on Twitter as @BroomOwl, over on his personal blog or Andy also blogs every month for Diabetes UK.

For more diabetes advice, support and real-life stories, click the banner below to sign up to our mailing list…

About the Author

Andy Broomhead

Andy - Sheffield born and bred. Aspiring marathon runner, Twitter user, photographer and sports fan.

Away from writing his blog, he says he splits his time fairly equally between his family (particularly his daughter), following football (Sheffield Wednesday - for his sins), listening to music (any kind - even getting into dubstep a bit), photography and kicking about on Twitter.