Skin, healing and infections
High glucose blunts the immune response and slows healing. Which infections come round more often, why feet get separate attention, and what to report early.
Infections turn up more often with type 1, and wounds take longer to close, because glucose running high for long stretches works against both. It is one of the more useful things to understand early, because most of what it asks of you is noticing rather than doing.
- High glucose blunts the immune cells that deal with bacteria, so an infection gets a foothold it would not otherwise get.
- Over years it also damages small vessels and nerves, so less blood reaches the skin to repair it and less sensation notices the damage.
- Infections that keep coming back, particularly fungal ones, can be a signal that glucose has been high rather than bad luck.
- Feet get separate attention because reduced sensation means an injury can go unnoticed for days.
- An infection also pushes glucose up, so being ill and being high tend to arrive together.
What high glucose does to healing
Two mechanisms, running on different timescales. In the short term, the white cells that hunt down bacteria work less efficiently when glucose is high, so something your body would normally deal with quietly gets established instead. That effect is not permanent and it improves as glucose does.
Over years, the second mechanism matters more. Persistently high glucose damages the smallest blood vessels, which are the ones supplying skin, so less blood and fewer repair materials reach a wound. It also damages nerves, which reduces sensation, so injuries are noticed later. Slower healing plus later noticing is a worse combination than either alone.
The honest framing is that this is a reason to pay attention, not a sentence. Neither mechanism is switched on by one bad week, and the second is the one your annual checks exist to catch early. Where it changes behaviour day to day is small: a cut is worth keeping an eye on rather than forgetting about.
The infections that come round more often
Fungal infections are the commonest. Thrush, athlete’s foot, and infections in warm skin folds all feed on sugar, and higher glucose gives them more to work with. They are treatable and usually straightforward, and the thing worth knowing is that repeatedly getting the same one is information rather than misfortune.
Bacterial ones show up too: boils, styes, infected hair follicles, and occasionally cellulitis, which is an infection spreading through the skin itself and needs treating promptly. Gum infections belong on the list as well, which is why dental care is more than cosmetic here and why a dentist is worth telling that you have type 1.
The pattern worth acting on is recurrence. Thrush that keeps returning, athlete’s foot that never fully clears, or a run of boils is a reasonable prompt to look at what glucose has been doing over those weeks, and to say so at your next appointment. In people not yet diagnosed, recurrent infections are one of the ways type 1 announces itself, which is the same signal seen from the other end.
What to report, and when it cannot wait
Feet get their own annual check for a specific reason. They are furthest from the heart, so blood supply is most affected; they lose sensation earliest; and they spend all day inside shoes where something rubbing goes unnoticed. A blister or a small cut that would be nothing anywhere else on the body is treated more seriously on a foot, and that is proportionate rather than alarmist.
So the rule people are given is simple: any break in the skin on a foot gets reported rather than watched. Looking at your feet regularly, including underneath and between the toes, is the whole practice, and it takes seconds. If sensation has changed at all, that goes to your team too, because it changes how carefully everything else needs doing.
Elsewhere on the body, the things worth getting seen without waiting are redness spreading outward, skin that is hot, swollen or increasingly painful, anything producing pus, and a wound that is not clearly healing after a few days. A fever alongside any of those means the same day rather than next week. And remember the other direction: an infection anywhere pushes glucose up and can push ketones up with it, so being unwell is exactly when your sick day plan matters and exactly when to use it. It does not always go that way, though. An illness that stops you eating, or that keeps you being sick, can make glucose drop instead, and a hypo while you are already unwell is harder to spot and harder to treat. That is why a sick day plan is agreed with your team in advance rather than worked out on the night.
What affects the risk
What glucose has been doing over months matters far more than any single day, which is why this belongs in the annual-check conversation rather than the daily one. Smoking is on the list because it narrows small blood vessels, which is the same supply this depends on. And heat and sweat are the everyday one, since fungal infections like warm damp skin.
How it shows up
Examples, not instructions or doses.
Treated three times in a few months. The recurrence itself is the signal, and it is worth mentioning at the next appointment rather than just treating again.
Something rubbing inside a shoe, unnoticed because sensation had reduced. This is exactly why feet are checked and why anything broken gets reported.
A small wound still open after a week with no obvious reason. Not healing is the thing to act on, rather than waiting to see.