Common causes of pain on the left side of the body include infection and injury to muscles, nerves, or internal organs, such as the heart, spleen, left lung or kidney, pancreas, and more.

Neck pain on the left side usually results from a benign cause, like muscle strain from sleeping in an awkward position. Sometimes, a more serious cause may be a tumor or rheumatoid arthritis.

If you have chest pain on the left side, your first thought may be that you’re having a heart attack. While chest pain can be a symptom of heart problems, that’s not always the case.