Red flag symptoms you should never ignore. Know when to call your doctor — and when you can relax.
More than 95% of chronic low back pain cases are not caused by a life-threatening condition. But catching the remaining 5% early matters a great deal.
An important note:
This page is not meant to frighten you. Knowing which symptoms are dangerous and which are not can spare you needless worry and help you act quickly when it matters.
What You'll Learn
- How often serious disease is found in people with low back pain (less often than you might think)
- The 7 warning signs ("red flags") you should never ignore
- Compression fractures from osteoporosis, especially important for older adults
- How to tell the difference between "call 911" and "schedule an appointment"
- Signs that family members and caregivers should watch for
1. When to Worry: The 7 Red Flags
Most Back Pain Is Not Dangerous
First, some reassuring facts.
A large review found that among patients who visited a hospital for low back pain, fewer than 5% had a serious underlying cause (Galliker 2019, American Journal of Medicine).
| Serious Cause |
Frequency |
| Vertebral fracture (broken bone in the spine) |
0–7.2% |
| Cancer metastasis (cancer spread to the spine) |
0–2.1% |
| Spinal infection (e.g., osteomyelitis, discitis) |
0–1.9% |
| Cauda equina syndrome (compressed nerve bundle) |
0.1–1.9% |
So out of 100 people who see a doctor for low back pain, more than 95 do not have a life-threatening condition.
For the remaining few, early detection can change lives, so it is important to know the warning signs below.
The 7 Red Flags
If you experience any of the following, see a doctor as soon as possible.
1. Leg Weakness
If you notice weakness in your foot or toes (difficulty lifting your foot, frequent tripping, or your shoe slipping off), these may be signs that a nerve is being compressed.
If the weakness is getting worse day by day, seek medical attention urgently.
2. Bladder or Bowel Problems
- Difficulty urinating, or loss of bladder control
- Loss of bowel control
- Numbness around the buttocks and groin area (the "saddle region")
These symptoms may indicate cauda equina syndrome, a condition where the bundle of nerves at the base of the spine is severely compressed.
Cauda equina syndrome is a spinal emergency. Surgery within 48 hours is recommended (Kohles 2004). If you notice these symptoms, call your doctor immediately or go to the emergency room.
3. Fever
If you have back pain along with a fever of 100.4°F (38°C) or higher, it could indicate a spinal infection (osteomyelitis, discitis, or epidural abscess).
You are at higher risk if you:
- Recently had a spinal injection or surgery
- Have diabetes
- Take steroids or immunosuppressive medications
4. Unexplained Weight Loss
If you are losing weight without dieting or trying to, over a period of weeks or months, it could be a sign of cancer or another systemic illness.
5. History of Cancer
If you have been treated for cancer in the past, new back pain should be evaluated to rule out metastasis (cancer spreading to the spine).
In patients with a history of cancer, spinal metastasis is found in approximately 33% of those who develop new back pain (Downie 2013, BMJ). This is a much higher rate than for any other red flag.
6. Night Pain
If your pain does not improve when you lie down and wakes you up in the middle of the night, take it seriously. Most back pain gets better with rest, but pain from infection or cancer may not respond to changes in position.
7. Pain After a Fall in Older Adults
If you are over 50 and develop back pain after a fall, a fracture should be considered. In people with osteoporosis, even a minor fall or landing hard on the buttocks can cause a broken bone.