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Most cancers do not announce themselves. They turn up as a cough that hangs around, a few kilos that slip off without explanation, a tiredness that a decent night’s sleep doesn’t touch. Ordinary complaints. That is exactly why so many people sit on them for months, telling themselves it’s nothing, and sometimes it isn’t.
Knowing the seven signs below won’t turn you into a diagnostician. It will make you harder to fumble. Because the single biggest factor in how treatable a cancer is often comes down to when somebody finally picked up the phone.
One thing before the list. None of these symptoms means you have cancer. Statistically, the overwhelming majority of people who notice them have something far more ordinary going on, from a lingering infection to a benign cyst to a stressful few months. What separates a nuisance from a signal is duration. A symptom that hangs around for three weeks or more, or one that steadily worsens, is the point at which waiting stops being reasonable. If you want the wider picture on how these diseases start and why early detection changes outcomes so much, what cancer actually is and what raises your risk is worth twenty minutes of your evening.
1. Weight loss you didn’t work for
Dropping a few kilos because you cut out beer and started walking to work is not a warning sign. Losing more than 5% of your body weight over six to twelve months, without changing anything about how you eat or move, is a different matter.
Doctors call it unintentional weight loss and they take it seriously, because it can point to cancers of the stomach, pancreas, oesophagus, lung or bowel. It also turns up in thyroid disease, diabetes, depression and a long list of digestive problems. That ambiguity is precisely why it’s a reason to start tests, not a reason to panic.
2. Tiredness that sleep doesn’t fix
There is a wide gap between the end-of-a-long-week tiredness and the kind that has you sitting down on the stairs. Cancer-related fatigue tends to be present when you wake, unrelieved by rest, and out of proportion to what you’ve done that day.
Blood cancers such as leukaemia and lymphoma often show up this way, sometimes alongside breathlessness on a short flight of stairs or an unusually pale look in the mirror. Fatigue is also the most common symptom of depression, and a hallmark of anaemia and thyroid trouble, so it rarely points in one direction. Mention it anyway. A simple blood test rules out a lot.
3. A lump, swelling, or thickening that sticks around
Most lumps are harmless. Breast cysts, harmless fatty lumps called lipomas, and lymph nodes that swell during a cold and shrink again within a fortnight are all extremely common. What deserves a look is a lump that stays put for three weeks or more, grows, feels hard and fixed rather than smooth and mobile, or comes with other symptoms.
The places people miss: the armpit, the base of the neck, the groin, and the collarbone. A persistent, painless swelling in any of those is worth pointing out to a GP even if you feel perfectly well. For a sense of where these lumps most often appear, this breakdown of the most common types of cancer and their signs is a useful reference.
4. Sores and moles that change or refuse to heal
A mouth ulcer that’s still there after three weeks is not a mouth ulcer you should ignore, particularly if it sits under the tongue or on the side, where people rarely look. The same goes for a scab or sore on the skin that never quite heals, or one that bleeds and crusts over repeatedly.
For moles, the dermatology shorthand of ABCDE is genuinely useful: Asymmetry, Border that’s ragged, Colour that’s uneven or changing, Diameter above 6mm, and Evolution, meaning anything that is visibly altering over weeks or months. A new dark streak under a fingernail or toenail counts too.
5. A cough, hoarse voice, or breathlessness that lingers
Coughs after a viral illness can drag on for weeks, and most settle on their own. A cough that lasts beyond three weeks, brings up blood, or comes with chest pain and unexplained weight loss needs investigating. So does a voice that has been hoarse for more than three weeks without a cold to explain it.
Some people find their breathing stays shallow long after a respiratory infection clears, which is common and usually benign; if that’s the pattern you’re dealing with, this guide to recovering from a respiratory infection covers what’s expected and what isn’t. The red flag is a change that keeps progressing rather than fading.
6. Blood where it shouldn’t be, or bowel and bladder changes
This one covers a lot of ground, and all of it deserves a mention:
- Blood in your stool, whether bright red or dark and tarry
- Blood in your urine, even once, even painless
- Any vaginal bleeding after menopause, or between periods
- Coughing or vomiting blood
- A bowel habit that has changed for three weeks or more: looser stools, more frequent trips, a feeling of not quite finishing
Bowel cancer in particular is easy to dismiss because the symptoms mimic irritable bowel syndrome, piles, or a dodgy week of eating. Piles are common. So is cancer, and the two can coexist.
7. Trouble swallowing or indigestion that keeps coming back
Food that feels like it’s sticking on the way down, or the need to wash each mouthful down with water, is a symptom people adapt to rather than report. They start eating more slowly, avoiding bread, cutting food smaller. That adaptation can hide a narrowing in the oesophagus for months.
New indigestion or heartburn in someone over 55, especially if it’s persistent, painful to swallow, or paired with weight loss, is a standard reason for further investigation. It’s rarely cancer. It’s also not something to treat with antacids for a year and hope.
The symptoms people worry about most, and what they usually mean
Plenty of frightening symptoms turn out to be mundane, and knowing that can save you a lot of sleepless nights:
- Isolated headaches with no other features are rarely a brain tumour; ones that wake you at night, worsen on coughing, or come with weakness or vision changes are the ones that need imaging.
- A swollen gland that shrinks within two weeks is almost always infection.
- Bright blood on the toilet paper with pain is very often a fissure or piles, though it should still be checked if it recurs.
- Chest pain is far more likely to be cardiac than cancer-related, and it should never be waited out. The signs of a heart attack and what to do in the first hour are worth knowing for exactly this reason.
How to get it checked without apologising for it
GPs see this every day. You are not wasting their time by booking a ten-minute appointment about a cough. A few things make the conversation more useful:
Write down dates. “It started around the middle of March and hasn’t gone away” is far more actionable than “it’s been a while.” Note anything that’s changed: weight, appetite, energy, sleep, bowel habits, and whether symptoms are getting better, staying flat, or worsening.
Mention everything, even the embarrassing bits. The blood, the change in the bathroom, the lump you found in the shower. Symptoms that seem unrelated often fit together, and the doctor can only join the dots you give them.
Ask directly about referral. In the UK, GPs work to clear guidelines about which symptom combinations warrant an urgent suspected cancer referral, usually with an appointment within two weeks. Asking “does this meet the criteria for a referral?” is a fair question and one most doctors welcome.
Turn up for screening. Bowel screening kits, cervical smears and mammograms catch cancers before they cause any symptom at all, which is why they outperform symptom-spotting every time. If you’ve been putting an invitation in a drawer, that drawer is the cheapest life insurance you own.
Three weeks. That’s the number to carry around with you. Most things settle before then. The ones that don’t are the ones worth a phone call, and the phone call takes less time than the worry.
