Back pain is the third most common reason for doctor’s visits and one of the most common reasons for missed days at work, according to the American Chiropractic Association.

A number of factors can cause pain on the left side of your middle back. Most causes aren’t serious.

Here’s a look at what could cause pain on the left side of your middle back and symptoms to look out for that may indicate a more serious problem.

Middle back pain refers to pain that occurs below the neck and above the bottom of the rib cage.

The area contains numerous bones, muscles, ligaments, and nerves. Pain can come directly from any of these. It can also come from nearby organs that can cause referred pain that’s felt in the middle back.

There are a number of bone and muscle issues that can cause middle back pain on your left side.

Muscle strain

A muscle strain occurs when a muscle is overstretched or torn. Heavy lifting or overworking your arms and shoulders can cause a muscle strain in your middle or upper back. When this happens, you may develop pain on one or both sides.

If you have a muscle strain, you may also notice:

Poor posture

Poor posture often places extra strain on your muscles, ligaments, and vertebrae. This extra strain and pressure can cause pain in your middle back.

Common examples of poor posture include:

  • hunching while using a computer, texting, or playing video games
  • standing with your back arched
  • slouching when sitting or standing

Other symptoms of poor posture include:

Osteoarthritis

According to the Centers for Disease Control and Prevention (CDC), more than 30 million people in the United States have osteoarthritis (OA). It develops when the cartilage within a joint begins to break down, usually over time due to wear and tear.

OA can affect any part of the spine and cause pain on one or both sides of the back. Other common OA symptoms include:

Pinched nerve

A pinched nerve can result from pressure that’s put on a nerve by surrounding tissues, such as cartilage, bone, or muscles. Depending on the location of the pinched nerve, you may feel pain on one side of your back.

Other symptoms may include:

Herniated disc

A herniated disc can occur when one of the discs between your vertebrae is injured and ruptures. That causes the inside disc gel to leak and protrude through the disc’s outer layer. Pain in the area of the affected disc is the most common symptom.

You may also have:

Spinal stenosis

Spinal stenosis is the narrowing of the spinal canal. It can place pressure on the spinal cord and nerves within. Aging most often causes it, such as aging associated with the degenerative process of OA in the spine.

Along with pain on one or both sides of your back, you may also have:

  • pain that radiates down one or both of your legs
  • neck pain
  • arm or leg pain
  • tingling, numbness, or weakness in your arms or legs

Myofascial painsyndrome

Myofascial pain syndrome is a chronic disorder in which pressure on trigger points in your muscles cause pain. The pain is felt in the muscles and can also radiate to other parts of the body.

A common cause is the repeated contraction of a muscle due to repetitive motions from sports or job activities. It can also be the result of muscle tension from stress.

Other symptoms may include:

Injury

An injury to any of the bones or tissues in your middle back can cause pain. Common causes of injuries are falls, sports-related injuries, and motor vehicle accidents. These can cause:

  • muscle strains and sprains
  • fractured vertebrae or ribs
  • herniated discs

Symptoms of a back injury depend on the exact location and severity of the injury. Pain from a minor injury usually improves within a week or two.

A more serious injury can cause severe pain that doesn’t go away over time and interferes with your daily activities.

Sometimes, pain felt on the left side of the middle back can be coming from a nearby organ.

Kidney stones

Kidney stones cause pain on one side of your body that also radiates to the upper abdomen. Pain may come and go depending on the size and location of the stone. It may be very intense at times.

If you have a kidney stone, you may also experience:

Gallbladder

Gallbladder and biliary tree problems can cause pain in your middle back, though some people feel it more to the right side.

There are several different types of gallbladder conditions that can cause pain. The symptoms you have will vary depending on the type of gallbladder issue.

The most common symptoms may include:

Though most gallbladder problems aren’t an emergency, some symptoms may indicate a gallbladder attack or biliary tree issue. Get to the emergency room right away if you experience:

  • chest pain
  • intense pain
  • high fever
  • yellowing of the skin

Pancreatitis

Pancreatitis is inflammation of the pancreas. It causes mid-left upper abdominal pain that can radiate to your back. The pain typically becomes worse after eating. It can be intense.

Acute pancreatitis comes on suddenly and can also cause:

Pancreatitis can become chronic and cause long-lasting symptoms, such as:

Heart attack

A heart attack is a medical emergency that can be fatal. It happens when the arterial blood supply that carries oxygen to the heart is severely blocked or stopped.

Not everyone who has a heart attack has obvious warning signs. Those that do, however, often have symptoms such as:

Call 911 or go to the nearest emergency room if you or someone else has warning signs of a heart attack.

The following are some self-care steps you can take at home to help relieve your middle back pain:

  • Apply heat or cold. Here’s how.
  • Take an over-the-counter pain medication, such as ibuprofen (Advil, Motrin) or naproxen (Aleve.)
  • Do gentle exercise, such as yoga, stretching, or walking.
  • Soak in an Epsom salt bath.
  • Pay attention to your posture. Avoid slouching or hunching.
  • Avoid sitting in one position for too long. It can cause your muscles to stiffen and weaken.

Middle back pain from minor injuries, such as a muscle strain, typically improve within a week or two with self-care. If your pain doesn’t get better within a couple of weeks or gets worse, follow up with your doctor.

Also see your doctor if you experience any tingling, pins and needles sensation, or numbness.

To diagnose the cause of your middle back pain, your doctor will ask about your medical history and symptoms. They’ll perform a physical exam. Your doctor may also perform a more specific neurological exam if you’re experiencing numbness and weakness.

Your doctor may also recommend one or more of the following tests:

Call 911 or go to the emergency room if you experience any of the following symptoms. These may be signs of a more serious medical condition:

  • chest pain, especially if accompanied by dizziness, sweating, nausea, or shortness of breath
  • pain that suddenly gets worse or is very different
  • sudden arm, leg, or face numbness or weakness
  • severe abdominal pain
  • high fever
  • loss of bladder or bowel control

Minor pain on the left side of your middle back isn’t usually a cause for concern. Simple home remedies and self-care should help ease the pain within a week or two.

If your pain is severe, doesn’t improve within a few days, or is accompanied by other concerning symptoms, make an appointment to see a doctor, or get immediate medical care.