Ask anyone about their immune system and they will answer with a frequency: they catch everything, or they never get ill. It is the wrong number to lead with. How often you meet an infection depends enormously on who you live with, whether you commute, and whether there are young children in the house — circumstances, not constitution. How long it takes you to recover is far less about exposure and far more about you.
The figure worth keeping
An ordinary upper respiratory infection takes most adults somewhere between seven and ten days to clear, with a cough that can trail on for two or three weeks after everything else has settled. That trailing cough is normal and is responsible for a great deal of unnecessary worry. What is worth noting is a drift: colds that used to take a week now taking a fortnight, or a chest that takes a month to feel normal when it used to take days.
The unglamorous inputs
Short sleep over weeks, sustained stress, heavy alcohol, and eating in a way that is thin on protein and on fruit and vegetables all measurably slow recovery. None of them are exciting and none of them can be bought. They are also the four that people are most likely to have changed without noticing, which makes them the first place to look when the recovery time has quietly doubled.
Where deficiency genuinely fits
Iron, B12 and vitamin D deficiencies produce a fatigue that is easily mistaken for a run of bad luck with infections, and all three are ordinary blood tests rather than guesses. The distinction matters: supplementing on suspicion treats a story, while testing treats a number. If tiredness has been the background note for months, it deserves the test rather than the shelf.
Age changes the shape, not just the speed
With age the immune response is slower to start and slower to stand down, which is why recovery stretches and why a straightforward infection can leave a longer tail of tiredness. It is also why the same illness can present less dramatically — a milder fever, a vaguer set of symptoms — and therefore be taken less seriously by everyone involved, including the person who has it.
Patterns that deserve a name rather than a shrug
Several infections in a row that each need antibiotics; the same site involved repeatedly; recovery that never quite completes before the next one starts; or weight coming off without trying alongside it. Any of those is a pattern rather than a bad winter, and patterns are worth describing in full rather than one appointment at a time.
What to raise, and when not to wait
Worth mentioning at a routine appointment: a recovery time that has clearly lengthened over a year or two, repeated infections in the same place, tiredness that has outlasted the illness by more than a month. Worth raising promptly: breathlessness at rest, a fever that will not settle, coughing up blood, or feeling markedly worse after appearing to improve. Getting ill is unavoidable. Taking three weeks to leave when it used to take one is the part that is worth a conversation.