Diagnosing sciatica 

Your GP will usually be able to confirm a diagnosis of sciatica based on your symptoms.

They will ask you what symptoms you experience, and which parts of your body are affected. Sciatica typically causes pain, numbness and a tingling sensation that radiates from the lower back and down one leg. Any pain in your lower back will generally be less severe than the pain in the affected leg.

A simple test known as the "passive straight leg raise test" can also help your GP identify whether you have sciatica.

This test involves lying flat on your back with your legs straight, and lifting one leg at a time. If lifting one of your legs causes pain or makes your symptoms worse, it is usually an indication that you have sciatica.

Warning signs

During your appointment, your GP will also ask you questions about anything in your medical history and individual circumstances that could indicate a potentially more serious cause of your symptoms, such as cauda equina syndrome, an infection of the spine, a spinal fracture, or cancer.

GPs refer to these warning signs as "red flags".

Red flags that suggest cauda equina syndrome include:

  • tingling or numbness between your legs and around your buttocks
  • recent loss of bladder and/or bowel control
  • weakness in your leg and foot 

Red flags that suggest cancer or infection include:

  • being over 50 or under 20 years of age
  • a history of cancer
  • symptoms of fever, chills or unexplained weight loss
  • having had a recent bacterial infection, such as a urinary tract infection (UTI)
  • having a history of injecting illegal drugs, such as heroin or cocaine
  • having a condition that weakens your immune system, such as HIV
  • a structural deformity of the spine

Red flags that suggest a spinal fracture include:

  • sudden severe pain in the spine which is relieved by lying down
  • recent major trauma, such as a road accident or fall from a height
  • minor trauma, including strenuous lifting in people with osteoporosis (weakened bones)
  • a structural deformity of the spine

Having one or more of these warning signs doesn't necessarily mean you have a serious condition, but it does mean a potentially more serious cause should be considered and investigated.

Therefore, if you have any red flags, your GP will probably refer you for further tests. If you have any warning signs that suggest cauda equina, they will make sure you are admitted to hospital immediately.

Further tests

Further tests are not usually necessary, unless a potentially serious cause of your symptoms is suspected.

In such cases, you may have a blood test to rule out infections and/or scans, such as a computerised tomography (CT) scan or a magnetic resonance imaging (MRI) scan to detect any problems with the nerves and structure of your spine.

Scans may also be carried out to examine your spine if surgery is being considered as a treatment option.

Read more about treating sciatica.

Page last reviewed: 26/08/2014

Next review due: 26/08/2016