Something I don’t hear or see discussed very often by diabetics is the symptoms and feeling of hyperglycaemia or high blood sugar. I think this is due to a combination of factors, most notably that they’re more subtle and harder to identify than hypoglycaemia, and for some people they may feel easier to deal with because they don’t have as immediate an affect. As for me, I’m one of the people who’s probably more scared of high blood sugars than low blood sugars because I know the complications and things that affect quality of life for diabetics (particularly vision and the nervous system) are more related to hyperglycaemia over longer periods of time. So I try to spend more time and attention on highs when looking at my blood sugar graphs than I do with hypos, and more time worrying about it overall. It’s frustrating then, that highs are so much more difficult to be aware of and deal with quickly than lows. Fast acting insulin is a huge and valuable part of this but knowing when you should or shouldn’t react to high blood sugar after eating a meal and working out the minutia of how much longer your blood sugar is likely to go up for is particularly difficult, and it’s frankly a long, drawn-out pain in the arse to deal with.
The top results on Google for hyperglycaemia symptoms all list thirst and urination but in my experience this tends to be only when you’ve had elevated blood sugar for at least an hour or two, or you’ve already drank a lot of liquids, and by this time some of the damage has already been done. Fatigue and headache are also common symptoms but I’ve never personally suffered or been aware of either. Finally blurred vision is listed and again, I don’t typically notice this or at least don’t think this describes it accurately enough. Instead I find my vision and mental focus narrowing the higher I get, almost like tunnel vision or narrowing vision with bright blurring around the edges, and brightness or white patches seems to become more noticeable, sort of like applying a saturation filter in Photoshop or having too much exposure in a photograph. Either way, this is still a late symptom for me and I’ll usually only begin to notice it when I’m above the 16mmol/l or 300mg/dl range, at which point other more noticeable symptoms like sweet/pungent breath, dry mouth and light headedness become apparent anyway.
Another late symptom I’ve noticed is listed as cramps, which apparently are quite common for others. This is probably my most recognisable symptom and quite consistent once I reach a certain high blood sugar stage. It feels like my muscles are pulling tighter and together, sort of like how I feel after a really short but hard and intense workout where l feel the effects of lactic acid seizing up my muscles. This makes sense in a correlative way considering lactate is used by the body in times of rapid stress on muscles (particularly lifting heavy weights and sprints) to aid short term in the use of glucose by the muscles, but that’s by the by.
It’s also important to know that the body tends to “acclimatise” in some ways to both high and low blood sugar over extended periods of time and false hypos where the symptoms of hypoglycaemia are felt but blood sugar is above a safe range, have been known about for a while. False hypos are talked about a bit more in depth here and has been studied in medicine briefly in the past. Suffice to say that it’s reasonable to assume that since hypo awareness is known to be increased when you’ve remained at an elevated blood sugar over a longer period of time, it’s reasonable to assume that the same and/or inverse are likely true, i.e. that hyper awareness may also be increased after remaining at a low or well controlled blood glucose level for a period of time. The takeaway is that keeping your blood sugar within the recommended range of 4.0 to 5.9 mmol/L or 70–99 mg/dL is the best thing you can do for awareness of highs, but that even this is unreliable or subtle at best in the early stages. There’s also the caveat that over time most diabetics tend to lose both hypo and hyper awareness to a degree and so this isn’t an option for many diabetics after a certain amount of time or a length of particularly bad control.
So what are some reliable early warning signs of high blood sugars? In short, I haven’t found any and unless you can afford the purported average of $20,000 (~£14,000) for a Diabetic Alert Dog or the current average of around £4,000/year for a CGM system then you’re going to have to rely on a combination of old fashioned regular testing, good control and lots of writing/recording your results. I find it frustrating having to leave something that damages my health over time in part to the whim of the cosmos, but like most things related to diabetes and life in general, the bigger picture is more important, and the better strategy is to plan and review until it becomes easier and takes less effort to manage while becoming less common.