9 reasons your lower left back hurts and when to see a doctor

Woman clutching lower left back in pain
If you have lower left back pain, it’s best to see a doctor in case of infection or a herniated disc. Povozniuk/Getty Images
  • The most common cause of low back pain on the left side is a muscle strain.
  • Other causes of lower left back pain include a kidney infection, herniated disc, and pregnancy.
  • To treat lower left back pain, take OTC pain relievers, improve your posture, and apply heat.
  • Visit Insider’s Health Reference library for more advice.

A stabbing or throbbing pain on the lower left side of your back can sideline you from exercise and basic activities for days. The good news is that it’s probably because you’ve strained some of your back muscles or ligaments, which will heal over time.

But in some cases, unilateral back pain, like on just the left side, signals a serious issue like an infection or injury that needs medical care.

Here are nine potential causes of pain on the left side of your lower back, when to consult a doctor, and how you can treat it yourself.

1. Muscle strain

The most common cause of lower left back pain is an injury to the muscles, tendons, and ligaments supporting the spine such as:

  • A fall or other accident causing back trauma
  • A sudden twisting movement
  • An uneven distribution of weight, such as when you’re carrying a heavy bag on one shoulder
  • Poor posture

Signs your back pain is due to a muscle strain is if you feel sore, stiff, experience a stabbing pain, or have muscle spasms, says Michael Rosner, MD, a neurosurgeon at George Washington University’s School of Medical and Health Sciences.

2. Infection

An advanced bladder infection or left kidney infection can cause a constant, aching pain that radiates through your left lower back.

If you have other symptoms such as burning urination, fever, or chills, see your doctor as soon as possible to check for an infection, says Anthony Chiodo, MD, clinical director of Spinal Cord Injury Medicine at the University of Michigan.

3. Kidney stones

Related Article Module: The major causes and risk factors for kidney stonesKidney stones, which are mineral build ups in your urinary tract, can cause sharp, intense pain through the lower left side of your back as well as pain in the lower abdomen, groin, and below the ribs. Another common symptom is bloody urine.

Smaller stones can pass through the urinary tract without treatment, but a urologist may need to remove larger stones via surgery or by using shock waves to break them up.

4. Endometriosis

Related Article Module: Symptoms of endometriosis and how you can manage the painEndometriosis is a condition where painful lesions grow on the outside of a person’s uterus. It can cause low left back pain, along with intense cramping during menstruation and pain during intercourse.

5. Stress fracture

Overtime repeated physical activity, such as lifting weights or playing sports like tennis, rowing, and gymnastics can strain the spine, resulting in a stress fracture.

The area may hurt when you touch it, and the pain may be too severe to respond to over-the-counter treatments. Most cases heal on their own in six to eight weeks, but the only way to get a proper diagnosis is through medical attention.

6. Pregnancy

More than two-thirds of pregnant women experience lower back pain, most often in the form of what is called posterior pelvic pain.

Posterior pelvic pain is a deep, throbbing pain that you either experience on one or both sides of your lower back.

You will also probably experience general muscle soreness in your back as the baby grows larger. That’s because the baby’s weight can throw off your center of gravity, which may require you to compensate by working different muscles in your back.

7. Sacroiliac joint dysfunction

Sacroiliac joint dysfunction is when the joint that connects the hip bones to the lower part of the spine moves abnormally, becoming inflamed.

Inflammation in the left hip joint can cause a dull, aching pain in the left lower back, often accompanied by pain in the buttocks, or in the back of the left upper thigh.

The condition can be chronic or a result of temporary stress. Risk factors include pregnancy, uneven leg length, or impact from an accident like a fall.

8. Herniated disc

Lumbar disks, the cushion of tissue between each vertebrae in the lower spine, can bulge or compress under stress, causing a herniated disc.

Most people have no symptoms from a herniated disc, but some develop pain and numbness on one side of their lower back, depending on where the disc is located. In rare cases, disks break or rupture, causing severe pain and requiring surgery to prevent permanent nerve damage.

“If you have radiating leg pain or increasing leg weakness, or bowel or bladder dysfunction, go to the emergency room,” Chiodo says.

9. Tumor

While rare, spinal cancer or a spinal tumor can cause back pain on the left or right side of the back.

Other symptoms may include unexplained weight loss, fever, numbness, weakness, or difficulty walking. However, it’s important to note that this is a rare cause of back pain.

Insider’s takeaway

Pain on the lower left backside is a common ailment and is usually the result of a soft tissue injury. Most back pain can be treated at home and should go away in a matter of weeks.

Having additional symptoms like fever or severe pain that persists for more than a few days may be a sign of a more serious underlying cause, such as a disk rupture, fracture, or an infection.

Consult your doctor as soon as possible if your arm or leg feels numb, you have problems walking or standing, or if you lose control of your bladder or bowels.

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