Approximately 84 percent of adults report having lower back pain at some point in their lives. The pain can be on one side of the spinal column or on both sides. The exact location of the pain can give clues about its cause.

Your lower back consists of five vertebrae. Discs between them cushion the bones, ligaments hold the vertebrae in place, and tendons attach muscles to the spinal column. The lower back has 31 nerves. As well, organs such as the kidneys, pancreas, colon, and uterus are located near your lower back.

All of these can be responsible for pain in the left side of your lower back, so there are many potential causes. While many require treatment, most aren’t serious.

There are many potential causes of lower back pain on the left side. Some are specific to that area, while others may cause pain in any part of the back. Common causes include:

Muscle strain or sprain

A muscle strain or sprain is the most common cause of low back pain.

A strain is a tear or stretching in a tendon or muscle, while a sprain is a tear or stretching in a ligament.

Sprains and strains usually happen when you twist or lift something improperly, lift something heavy, or overstretch your back muscles.

These injuries can cause swelling, difficulty moving, and back spasms.

Sciatica

Sciatica is pain caused by compression of the sciatic nerve. This is the nerve that runs through your buttocks and down the back of your leg.

Sciatica is usually caused by a herniated disc, bone spur, or spinal stenosis compressing part of the sciatic nerve.

Sciatica usually only affects one side of the body. It causes an electric or burning low back pain that radiates down your leg. The pain may get worse when you cough, sneeze, or sit for a long time.

Serious causes of sciatica can cause weakness and numbness in your leg.

Herniated disc

A herniated disc occurs when one or more of the discs between your vertebrae get compressed and bulge outward into spinal canal.

These bulging discs often push on nerves, causing pain, numbness, and weakness. A herniated disc is also a common cause of sciatica.

Herniated discs can be caused by an injury. They also become more common as you age, because the discs naturally degenerate. If you have a herniated disc, it’s likely you’ve had recent low back pain.

Osteoarthritis

Osteoarthritis is when the cartilage between your vertebrae starts to break down. The lower back is a common site of osteoarthritis, because of the stress of walking.

Osteoarthritis is usually caused by normal wear and tear, but previous back injuries can make it more likely.

Pain and stiffness are the most common symptoms of osteoarthritis. Twisting or bending your back may be especially painful.

Dysfunction of sacroiliac joints

Dysfunction of the sacroiliac (SI) joints is also called sacroiliitis. You have two sacroiliac joints, one on each side of your spine where it connects with the top of your pelvis. Sacroiliitis is inflammation of this joint. It can affect one or both sides.

Pain in your lower back and buttocks is the most common symptom. The pain is usually made worse by:

  • standing
  • climbing stairs
  • running
  • putting too much weight on the affected leg
  • taking large steps

Kidney stones or infection

Your kidneys play a vital role in flushing waste from your body. Kidney stones may form in these organs. These stones can result from different causes, such as a buildup of waste or not enough fluid in your kidneys.

Small kidney stones may not cause any symptoms, and may pass on their own. Larger stones, which may require treatment, can cause these symptoms:

A kidney infection usually starts as a urinary tract infection (UTI). It causes most of the same symptoms as kidney stones. If not treated, a kidney infection can permanently damage your kidneys.

Endometriosis

Endometriosis occurs when the type of cell that makes up the lining of your uterus grows outside the uterus. These cells can swell and bleed every month when you get your period, which causes pain and other issues.

Endometriosis is most common in women in their 30s and 40s.

Pain is the most common symptom, including:

Other symptoms include:

Fibroids

Fibroids are tumors that grow in the wall of the uterus. They are usually benign.

Symptoms of fibroids include:

  • heavy bleeding during periods
  • painful periods
  • lower abdominal bloating
  • a full feeling in your lower abdomen
  • low back pain
  • frequent urination
  • pain during sex

Other potential causes of low back pain on the left side

Pancreatitis and ulcerative colitis can both cause low back pain. However, this is a rare symptom of both. When they do cause back pain, it’s usually higher in the back. Both conditions should be treated as soon as possible by a doctor.

Back pain is very common throughout pregnancy. This may be because of:

  • the heavier front of your body straining back muscles
  • posture changes
  • your abdominal muscles weakening as your stomach grows, which means your spine isn’t as well supported
  • sciatica
  • hormones causing the ligaments in your pelvis to relax, to prepare for birth (f they become too mobile, this can cause pain)
  • SI joint dysfunction
  • kidney infection (if the urinary tract infections that are more common in pregnancy aren’t treated properly)

While many causes of lower back pain can be healed with time and over-the-counter remedies, some can require medical attention. See a doctor if you have:

  • pain that doesn’t get better after a few weeks
  • numbness, tingling, and weakness, especially in your legs
  • issues controlling your bowels
  • trouble urinating
  • severe pain, especially if it’s sudden
  • fever
  • unexplained weight loss
  • pain after a fall or injury

To diagnose lower back pain, a doctor will first do a physical exam. They’ll look at how well you move and if your back has any visible issues.

Then they’ll take a medical history. This will cover your symptoms, any recent injuries, previous back issues, and the severity of your pain.

A physical exam and medical history are often enough for a doctor to determine the cause of your pain. However, they may also need to do an imaging test. Potential tests include:

  • X-ray, which can find broken or misaligned bones.
  • CT scan, which shows soft tissues such as the discs between vertebrae and potential tumors
  • myelogram, which uses dye to enhance the contrast in a CT scan or X-ray to help a doctor identify nerve or spinal cord compression
  • nerve conduction test if the doctor suspects nerve issues
  • bone scan to see if you have any bone issues (not used as commonly as X-ray)
  • ultrasound to look more closely at soft tissues (not used as commonly as CT scans)
  • blood tests if the doctor suspects an infection
  • MRI scan if there are signs of a serious problem

In general, there’s not a lot of evidence for treatments for low back pain not caused by a specific issue. In many cases, time, rest, and pain relievers will help. Other issues need medical attention and treatment.

Unless you have signs of a serious condition or have a recent injury, you can often try at-home remedies first and then see a doctor if you still have pain.

Self-care

Home treatments may include:

Medical treatment

Medical treatment may vary depending on the cause of the pain. Potential treatments include:

Lower back pain on your left side, above the buttocks, has many potential causes. Many can be treated with home remedies. But others can be serious.

If you’ve had a recent injury, have numbness or weakness in your legs, have signs of an infection, or experience pain that seems connected to your menstrual cycle, call a doctor.