Cold or Flu on Scan Day: Should You Still Go to Your Appointment?

Winter viruses do not check your diary. Every year some scan appointments fall on the one morning the patient wakes up with a cold, and this year the collision may come early: the UK Health Security Agency said on 8 October that early signs suggest flu season may be starting earlier this year.

Most colds do not stop a scan. Some symptoms do, and a few make the scan hard to do well. This guide sets out the NHS advice on being unwell around other people, the problems a cough causes, what to tell the clinic about contrast and fluids, and the scans you should not quietly push back.

The rule the NHS gives

The NHS flu page says to try to stay at home and avoid contact with other people if you have a high temperature, feel hot, cold or shivery, or do not feel well enough to do your normal activities. The NHS common cold page says you are infectious until all your symptoms have gone, which usually takes 1 to 2 weeks, and that if you have a high temperature or cannot manage your normal activities you should try to stay at home and avoid contact with others until you feel better.

That is a useful test for a scan appointment. If you would stay off work with these symptoms, the same reasoning applies to a waiting room. The NHS flu page lists being 65 or over, being pregnant, having a long-term condition and having a weakened immune system among the reasons to get urgent advice about flu symptoms, and those are exactly the people who fill imaging departments. A cold with no temperature is usually just an inconvenience. If you attend with mild symptoms, the NHS steps that stop a cold spreading apply: wash your hands often, use tissues when you cough or sneeze, and bin them quickly.

Why this autumn is different

The UKHSA blog of 8 October said that two influenza A subtypes, H1N1 and H3N2, are circulating in England, that September activity was higher than in the past four winters although still at baseline, and that the rise so far has been driven largely by people aged 18 to 24. Its advice was to get vaccinated sooner rather than later, because it takes a couple of weeks for the vaccine to provide full protection. The NHS says flu is most infectious in the first 5 days, and an early season means more appointments land in that window.

A cough and an MRI

The NHS says an MRI scan usually takes between 15 minutes and 1 hour, that you will need to lie still so the scanner can take clear images, and that you may be asked to hold your breath during parts of the scan. A chesty cough works against all three. Every cough moves the part of the body being scanned, and a sequence spoiled by movement has to be repeated, which makes a long scan longer. For a scan of the head, neck or chest the problem is worst, and breath-holds are hard with a tight chest.

A blocked nose matters for a different reason: people who are already anxious about the scanner find it harder to relax when they cannot breathe easily through the nose. None of this is dangerous; it simply means a worse scan or a wasted slot. If your cough is bad enough to interrupt a conversation, tell the clinic before you set off. Many would rather move you a week than scan you twice. Our guide to what to expect at an MRI describes the scan itself.

Contrast, fluids and feeling unwell

Some MRI and CT scans use a contrast dye to show more detail. The NHS says that before an MRI you will be asked about things such as kidney problems, allergies including to contrast dye, and whether you may be pregnant; before a CT scan it says to tell the hospital if you have kidney or thyroid problems, diabetes, or have reacted to contrast before. A cold does not change any of that, but being properly ill can. The NHS common cold advice is to drink plenty of fluids to avoid dehydration; if you have been vomiting or unable to keep fluids down, say so, because the clinic may want you well hydrated before a contrast injection.

Fasting adds another layer. The NHS says that for some CT scans you may be asked not to eat for several hours beforehand. If you are feverish and struggling to eat anyway, a fasting scan on top is a reason to phone rather than soldier on. Our guides to MRI with contrast and eating and drinking before a scan go into the detail.

Scans you should not quietly put off

Moving a routine scan by a week or two is rarely a problem. Some scans are not routine. If a clinician asked for the scan urgently, if it is part of an NHS pathway with a deadline, or if it is a follow-up to check on something already found, speak to the clinician who referred you, or to the clinic, before moving it. They can tell you whether a short delay matters. That is a conversation to have, not a decision to make alone at 7am.

Being ill also has its own red flags that take priority over any appointment. The NHS says to call 999 or go to A&E if you get sudden chest pain, have severe difficulty breathing or start coughing up blood, and to ask for an urgent GP appointment or contact NHS 111 if you feel very unwell or short of breath, if your symptoms have not improved after 7 days, or if you are in a higher-risk group with flu symptoms. A scan can wait for those; they cannot wait for a scan.

Rearranging your appointment

The clinic carrying out your scan is the one to contact if you fall ill, because it manages its own appointments and its own cancellation terms. Call as soon as you know you are unwell, not when you arrive, because a slot released early can usually be given to someone else. If your scan is an NHS appointment, use the number on your hospital letter. Our guide to postponed NHS scan appointments covers what happens when the hospital moves it instead.

If you have not yet chosen a clinic, you can compare clinics and send an enquiry; the clinic contacts you, so you can mention any symptoms then. FindScan is a directory of independent, regulated imaging clinics: you compare clinics and send an enquiry, and the clinic contacts you. We are not a healthcare provider, and nothing here replaces advice from the clinician who requested your scan or from the clinic carrying it out.