Call your doctor promptly if:
You hear or feel a pop in your muscle at the time of injury.
You have severe pain, swelling or discoloration in the injured muscle.
Your injured muscle is obviously weak or has difficulty moving compared to the same muscle on the opposite side of your body.
You have mild muscle symptoms that do not improve after 48 hours.
You have severe back pain that makes it impossible for you to do normal daily activities, or you have mild back pain that worsens after a few days.
You are being treated for a strained back and your symptoms do not improve within two weeks.
You have back pain together with any of the following symptoms, which can signal a medical problem that is more serious than a mild back strain:
Fever or chills
Pain or a burning feeling when you urinate
Sudden weakness, numbness or tingling in a leg
Numbness in your groin or rectum
Difficulty controlling your bladder or bowel function