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Part of Low back pain

When is back pain serious? The warning signs and how fast to act

Serious back pain is rare: in a study of 1,172 people seen in primary care with new low back pain, fewer than 1 in 100 turned out to have a serious cause, and most of those were fractures of the spine. Back pain becomes serious when it comes with certain other signs, and some of them cannot wait. Numbness around your genitals or bottom, new trouble with your bladder or bowels, pain, tingling, numbness or weakness in both legs, or loss of feeling in one leg means calling emergency services or going to an emergency department straight away. Back pain after a serious accident or with chest pain, or sudden, severe back or tummy pain with feeling faint or clammy skin, means calling emergency services. If you have had cancer, back pain with weakness, numbness, tingling or trouble walking is also an emergency. Back pain with a fever together with new leg weakness, numbness or tingling, or new bladder or bowel trouble, is an emergency too. Others, such as back pain with a fever alone, weight you have lost without trying, or new back pain when you have had cancer, mean getting medical advice the same day. This page sorts every sign by how fast to act and explains what each one can mean.

Warning signs, and when to get help

When is back pain serious, and how rare is it?

Very rare, which is worth knowing before reading a list of frightening possibilities. A Lancet review describes most low back pain as non-specific: for nearly everyone, no single damaged structure explains the pain, and only a small minority have a serious cause such as a fracture, cancer or an infection (Hartvigsen and colleagues, 2018).

One Australian study put a number on it. Researchers followed 1,172 people seen in primary care with new low back pain. Eleven of them, under 1 percent, had a serious cause: 8 spinal fractures, 2 cases of inflammatory arthritis and 1 case of cauda equina syndrome (Henschke and colleagues, 2009). The same study found that 80 percent of people had at least one so-called red flag, which shows that a single warning feature on its own is common and usually harmless.

That is why clinicians do not read warning signs as a checklist. The international red flag framework, published in 2020, asks clinicians to weigh them alongside the whole history and an examination, because good evidence on how accurate most single red flags are is lacking (Finucane and colleagues, 2020). For you, the practical message is simpler: know the handful of signs that cannot wait, and know how fast to act on each.

When is back pain an emergency?

Eight patterns mean emergency care. If one of them fits you, act on it now and come back to this page later. The warning list at the end of the page gives each one in full, with the exact action.

The first three involve the bundle of nerves at the base of the spine (the cauda equina), which controls the bladder, bowel and sexual function and gives feeling to the skin around the genitals and bottom. Pressure on it can cause numbness in that saddle area, new trouble peeing or controlling your bowels, or symptoms in both legs, and it needs emergency treatment. NHS England's national cauda equina pathway explains why speed matters: the longer the nerves stay squashed, the worse the bladder tends to recover, and results are worse once someone can no longer pee and does not feel it, so surgeons aim to relieve the pressure before that stage. NHS hospital guidance warns that if it is missed or treated late, it can leave lasting problems with the bladder, bowel, sexual function or legs. Numbness around your genitals or bottom, new trouble with your bladder or bowels, pain, tingling, numbness or weakness in both legs, or loss of feeling in one leg means calling emergency services or going to an emergency department straight away.

Back pain after a serious accident, such as a car crash or a fall from a height, means calling emergency services, and if it came on straight after the accident, keep still while you wait (NICE NG41). Back pain that comes with chest pain also means calling emergency services, since the cause may not be in the back at all. People with a stiff spine condition such as ankylosing spondylitis are a special case: their spine can break after a small knock, so new pain after even a minor fall or jolt means calling emergency services or going to an emergency department straight away, without driving yourself, and telling the staff about your spine condition. If the pain started straight after the injury, or you also have numbness, tingling or weakness in your arms or legs, keep still where you are and call emergency services.

The main blood vessel in the tummy (the aorta) can also cause back pain. If it has a weak, swollen section (an abdominal aortic aneurysm) and that bursts, the pain in the lower back or tummy is sudden and severe, and it can come with feeling faint, clammy skin or being short of breath. It is rare, and more likely in people over 60, people who smoke or used to smoke, people with high blood pressure and anyone already told they have an aneurysm (NICE NG156). If you are in one of those groups and get sudden, severe back or tummy pain that is not like your usual back pain, call emergency services. Anyone whose sudden, severe back or tummy pain comes with feeling faint, clammy skin, a racing heartbeat or being short of breath should do the same, whatever their age (NHS).

The seventh is for anyone who has had cancer. Back pain that feels like a tight band around the body, or comes with weakness, numbness or pins and needles in the arms or legs, trouble walking or trouble with the bladder or bowels, can mean cancer is pressing on the spinal cord. UK guidance treats this as an emergency (NICE NG234). The action is to call your cancer team's emergency number straight away, or go to an emergency department if you do not have one or cannot get through.

The eighth is infection. Back pain with a fever, or feeling hot, shivery or very unwell, together with new weakness, numbness or tingling in a leg, or new trouble with your bladder or bowels, can mean a collection of pus is pressing on the nerves in the spine (spinal epidural abscess). Found late, it can leave lasting weakness or paralysis (Darouiche, 2006), so call emergency services or go to an emergency department straight away.

Which back pain needs a doctor the same day?

Same day means getting medical advice today, from your own doctor, an urgent care center or a phone advice line, rather than waiting for a routine appointment. Six signs sit here.

A foot that drags, catches or slaps down as you walk (foot drop) usually means a nerve in the lower back or leg is not working properly: get medical advice the same day, and if the weakness is getting worse by the hour, go to an emergency department. If you are older, have low bone density (osteoporosis) or have taken steroid tablets for a long time, back pain after a minor fall or strain means getting medical advice the same day, because the spine can break with little force; fractures were the commonest serious cause in the Australian study above. Back or leg pain with a fever, or feeling hot, cold, shivery or generally unwell, can point to an infection: get medical advice the same day, and go to an emergency department if you feel very unwell. A spinal infection does not always cause a fever, and it is more likely if you have recently had spine surgery or an injection into your spine, inject drugs, or take medicine that weakens your immune system (Finucane and colleagues, 2020). If you have had spine surgery or a spinal injection in the last three months, contact your surgical team the same day about a fever, a wound that is red, hot, swollen or leaking, or back pain that is new or much worse, even without a fever.

Back pain with weight you have lost without trying, or new back pain when you have had cancer at any time, means getting medical advice the same day, because rarely it can mean cancer has spread to the spine. Mention the weight loss or the cancer history, since it changes what the doctor looks for, and if you are being treated for cancer now, contact your cancer team the same day. The sixth is severe pain that comes on suddenly or keeps getting worse quickly, which also means getting medical advice the same day. The warning list below gives the full wording for each, including when to go to an emergency department instead.

What can wait a few days or weeks?

Pain that is worse at night, or does not ease at all when you rest, means seeing your doctor within a few days. If you have had cancer or have lost weight without trying, get medical advice the same day instead, and contact your cancer team the same day if you are being treated now. Night pain on its own is common with ordinary back pain, especially stiffness when you turn over, so sleeping positions for back pain is a useful next read.

Back or buttock pain that started before 45, has lasted more than three months, is worse after rest and in the morning, and eases when you move can be inflammatory back pain (axial spondyloarthritis) rather than the ordinary kind. NICE asks doctors to refer people whose back pain began before 45 and has lasted more than three months to a rheumatologist when several other features are also present, such as buttock pain, waking in the second half of the night because of the pain, or pain that gets better with movement (NICE NG65). It is not an emergency, but see your doctor in the next week or two. The ankylosing spondylitis page explains the condition.

What about back pain that is just not getting better?

That is a routine reason to book an appointment rather than a warning sign. See a physio or doctor if your back is not improving after a few weeks, if it stops you working or sleeping, or if you are worried about it. How long does back pain last has a section on when back pain has gone on too long, and should I rest or move covers what to do meanwhile.

Ache in a leg that has built up slowly, comes on as you walk and eases when you sit is also routine, but still needs a doctor's check, because the cause may be a narrowed spinal canal or narrowed arteries in the legs. If a doctor has not checked it, book an appointment with your doctor, and see your doctor within a few days if the distance you can walk has become much shorter over a few weeks; see is walking good for lower back pain and the spinal stenosis program. Pain, tingling, numbness or weakness in both legs is different: it is on the emergency list. If a doctor has already told you that you have spinal stenosis, its page explains which changes in both legs are its usual pattern and which are an emergency. Pain that runs below the knee into one leg, with or without pins and needles, is usually an irritated nerve, and the sciatica page covers it.

How doctors and physios check for serious causes

Expect questions that seem unrelated to your back: your age, any history of cancer, recent weight change, fever, steroid use, falls, and your bladder and bowels. They are routine screening, not a sign that anyone suspects something. For most people the answers point to ordinary back pain, and the next step is usually advice, exercise and time, as in the low back pain program.

If you are managing at home, back pain at work covers staying at or getting back to work, exercises to avoid covers what to hold off on for now, and heat or ice covers the most common home remedy question. The warning list below is the one to keep handy.

Related exercise programs

Warning signs

Get emergency help now

  • Emergency: numbness, tingling or altered feeling around or under your genitals, between your inner thighs, or around your bottom (anus), for example it feels different when you wipe after using the toilet. Call emergency services or go to an emergency department straight away. This can be a sign of pressure on the bundle of nerves at the base of the spine (cauda equina syndrome), which needs emergency treatment.
  • Emergency: you find it hard to start peeing, cannot pee, cannot feel yourself peeing or cannot control when you pee, or you do not notice when you need to poo or cannot control when you poo, and this is not normal for you. The same applies to a new change in how your genitals feel during sex, or new trouble getting an erection or ejaculating. Call emergency services or go to an emergency department straight away. These can also be signs of cauda equina syndrome.
  • Emergency: sciatica in both legs, or pain, tingling, numbness or weakness in both legs. The same applies if you lose feeling in one leg. Call emergency services or go to an emergency department straight away.
  • Emergency: back or leg pain that started after a serious accident, such as a car crash or a fall from a height, or back pain with chest pain. Call emergency services. If the pain started straight after the accident, keep still while you wait.
  • Emergency: sudden, severe pain in your lower back or tummy that is not like your usual back pain, if you have been told you have a swelling of the main blood vessel in your tummy (abdominal aortic aneurysm), you are over 60, you smoke or used to smoke, or you have high blood pressure. The same applies if sudden, severe back or tummy pain comes with feeling faint or passing out, pale, sweaty or clammy skin, a racing heartbeat or being short of breath. Call emergency services straight away. This can be a sign of an aneurysm bursting, which needs treatment in hospital at once.
  • Emergency: new neck or back pain after a fall, a knock or a jolt, even a minor one such as a trip or a sudden stop in a car, if you have a condition that stiffens the spine, such as ankylosing spondylitis. Call emergency services or go to an emergency department straight away, do not drive yourself, and tell the staff about your spine condition, so they keep your neck and back in their usual position. A stiff spine can break after a small injury, and the break is easy to miss at first. If the pain started straight after the injury, or you also have numbness, tingling or weakness in your arms or legs, keep still and call emergency services.
  • Emergency: you have had cancer, now or in the past, and your back or neck pain feels like a tight band around your body, or comes with pain spreading down an arm or leg, weakness, numbness or pins and needles in your arms or legs, trouble walking, or trouble controlling your bladder or bowels. Call your cancer team's emergency number straight away, or go to an emergency department if you do not have one or cannot get through. This can be cancer pressing on the spinal cord (metastatic spinal cord compression), which needs treatment straight away.
  • Emergency: back pain with a fever, or you feel hot, shivery or very unwell, and you also have new weakness, numbness or tingling in one or both legs, or new trouble with your bladder or bowels. Call emergency services or go to an emergency department straight away. This can be an infection pressing on the nerves in the spine (spinal epidural abscess), which needs emergency treatment.

Get help today

  • Same day: a leg or foot that is getting weaker, for example your foot drags, catches on the ground or slaps down when you walk (foot drop). Get medical advice the same day. If the weakness is getting worse by the hour, go to an emergency department.
  • Same day: back pain after a minor fall or strain if you are older, have low bone density (osteoporosis) or have taken steroid tablets for a long time. Get medical advice the same day.
  • Same day: back or leg pain with a fever, or you feel hot, cold, shivery or generally unwell. Get medical advice the same day, and go to an emergency department if you feel very unwell.
  • Same day: you have back pain and have lost weight without trying. Get medical advice the same day and mention the weight loss.
  • Same day: new back pain and you have had cancer, now or in the past. Get medical advice the same day and mention your cancer history. If you are being treated for cancer now, contact your cancer team the same day.
  • Same day: severe pain that comes on suddenly or is getting worse quickly. Get medical advice the same day.
  • Same day: pain that is worse at night, or does not ease at all when you rest. If you have had cancer, now or in the past, or you have lost weight without trying, get medical advice the same day.

Book an appointment

  • Within a few days: pain that is worse at night, or does not ease at all when you rest. See your doctor within a few days.
  • Within a week or two: back or buttock pain that started before the age of 45, has lasted more than three months, is worse after rest and in the morning, and eases when you move. This is not an emergency, but see your doctor in the next week or two and ask whether it could be inflammatory back pain (axial spondyloarthritis).
  • Routine: pain or aching in a leg that comes on when you walk and goes after a few minutes' rest, and a doctor has not checked it yet. Book an appointment with your doctor. Narrowed arteries in the legs (peripheral arterial disease) can cause this too, and they need different treatment. If the distance you can walk before the pain starts has become much shorter over a few weeks, see your doctor within a few days. Pain, tingling, numbness or weakness in both legs is on the emergency list above.

Common questions

Is back pain usually serious?

No. In a large Australian study of people seen in primary care with new low back pain, 11 of 1,172 (0.9 percent) had a serious cause, and 8 of those 11 were fractures (Henschke and colleagues, 2009). Most back pain is non-specific, which means no single damaged structure can be found, and it usually improves a lot over the first few weeks. Knowing the warning signs means the rare serious cause gets found quickly.

Do I need a scan to check my back pain is not serious?

Usually not. NICE advises against routine imaging for low back pain outside specialist care. Scans often show disc bulges and wear changes in people with no pain at all, and these become more common with age (Brinjikji and colleagues, 2015), so a scan can worry people without changing what helps. Doctors arrange one when the history or examination suggests a serious cause, or when the result would change the treatment.

Why does my back hurt more at night?

Often for ordinary reasons: lying still for hours stiffens a sore back, and turning over can catch it. That kind of night pain usually eases once you are up and moving. The warning sign is different: pain that is worse at night, or does not ease at all when you rest, even when you change position. See your doctor within a few days. If you have had cancer, now or in the past, or you have lost weight without trying, get medical advice the same day. If you are being treated for cancer now, contact your cancer team the same day.

Can a physio tell if back pain is serious?

Physios are trained to screen for serious causes and to refer on when something does not fit. The international red flag framework used by physios and other clinicians was led by the international body for orthopedic manual physical therapists (Finucane and colleagues, 2020). It treats warning signs as part of the whole picture, alongside your history and an examination, rather than a checklist on its own. If something needs a doctor or a scan, a physio will tell you how quickly.

References

  1. Henschke N, Maher CG, Refshauge KM, et al. Prevalence of and screening for serious spinal pathology in patients presenting to primary care settings with acute low back pain. Arthritis and Rheumatism. 2009;60(10):3072-3080. https://doi.org/10.1002/art.24853
  2. Hartvigsen J, Hancock MJ, Kongsted A, et al. What low back pain is and why we need to pay attention. The Lancet. 2018;391(10137):2356-2367. https://doi.org/10.1016/S0140-6736(18)30480-X
  3. Finucane LM, Downie A, Mercer C, et al. International framework for red flags for potential serious spinal pathologies. Journal of Orthopaedic and Sports Physical Therapy. 2020;50(7):350-372. https://doi.org/10.2519/jospt.2020.9971
  4. National Institute for Health and Care Excellence. Low back pain and sciatica in over 16s: assessment and management (NG59). Published 2016, last updated July 2026. https://www.nice.org.uk/guidance/ng59
  5. National Institute for Health and Care Excellence. Spinal metastases and metastatic spinal cord compression (NG234). Published September 2023. https://www.nice.org.uk/guidance/ng234
  6. National Institute for Health and Care Excellence. Spondyloarthritis in over 16s: diagnosis and management (NG65). Published February 2017. https://www.nice.org.uk/guidance/ng65
  7. NHS. Back pain. https://www.nhs.uk/conditions/back-pain/
  8. NHS. Abdominal aortic aneurysm. https://www.nhs.uk/conditions/abdominal-aortic-aneurysm/
  9. National Institute for Health and Care Excellence. Abdominal aortic aneurysm: diagnosis and management (NG156). 2020. https://www.nice.org.uk/guidance/ng156
  10. Royal Cornwall Hospitals NHS Trust. Emergency department cauda equina syndrome pathway. Clinical guideline. https://doclibrary-rcht.cornwall.nhs.uk/DocumentsLibrary/RoyalCornwallHospitalsTrust/Clinical/EmergencyDepartment/EmergencyDepartmentCaudaEquinaSyndromePathwayClinicalGuideline.pdf
  11. Getting It Right First Time (GIRFT), NHS England. National suspected cauda equina syndrome (CES) pathway. February 2023, updated March 2026. https://gettingitrightfirsttime.co.uk/wp-content/uploads/2026/04/National-Suspected-Cauda-Equina-Pathway-March-2026.pdf
  12. Darouiche RO. Spinal epidural abscess. New England Journal of Medicine. 2006;355(19):2012-2020. https://doi.org/10.1056/NEJMra055111
  13. National Institute for Health and Care Excellence. Spinal injury: assessment and initial management (NG41). Published February 2016. https://www.nice.org.uk/guidance/ng41
  14. Torbay and South Devon NHS Foundation Trust. Cauda equina syndrome (CES). https://www.torbayandsouthdevon.nhs.uk/services/specialist-spinal-orthopaedic-physiotherapy-service/common-spinal-conditions/cauda-equina-syndrome/
  15. Brinjikji W, Luetmer PH, Comstock B, et al. Systematic literature review of imaging features of spinal degeneration in asymptomatic populations. American Journal of Neuroradiology. 2015;36(4):811-816. https://doi.org/10.3174/ajnr.A4173

Written and checked by the PocketPhysio editorial team. Last updated 2026-10-16.

This page is general education, not a diagnosis or a personal treatment plan. See a physiotherapist or doctor for advice about your own situation.