Though a stabbing pain in the chest when lying on the left side can be caused by muscle, it can also be caused by a heart problem.

“Stabbing chest pains can arise from the heart, the lungs, the GI system or the musculoskeletal system,” says Nichole M. Polin, MD, FACC, Director, Cardio-Oncology Clinic, Ochsner Health System.

“Positional discomfort such as when a person lies on their left side typically occurs from musculoskeletal pain or from indigestion,” continues Dr. Polin.

The key variable here is change in body position. If there’s something wrong with a pectoralis muscle (e.g., strain from working out earlier in the day), doesn’t it stand to reason that this would be the cause of stabbing pain in the chest that occurs only when you lie on or turn towards your left side?

This could be triggering a spasm or a pulling of an injured muscle. Spasms can hurt quite a bit but typically do not last long.

Dr. Polin continues, “It can also occur when inflammation is present around the heart [pericarditis] or the lungs.

“If the pain worsens with inspiration [breathing in] or movement, it is unlikely to be caused by a serious blockage in the coronary arteries.”

If your coronary arteries are clogged, ask yourself why this would cause pain upon movement.

The coronary arteries have no idea when the body is moving.

Pain from coronary artery blockages is not caused by turning over on one’s side.

The pain is caused by inadequate blood flow to the heart, thanks to the plaque buildup in the arteries causing a reduced diameter through which the blood flows.


This has nothing to do with turning over on one’s side, though the cardiac ischemia from blocked coronary arteries can definitely occur on the left side. It’s just that movement does NOT trigger it.

“If other symptoms are present such as fever, excessive sweating or shortness of breath, medical attention should be sought,” says Dr. Polin.

“Otherwise, one can try an antacid or an over the counter anti-inflammatory medication such as ibuprofen.”

Next time you experience bad chest pain upon turning over onto your left side, take inventory of any other nearby area where there is discomfort – even if it’s only mild discomfort.

The anxiety over the chest pain may be masking your perception of something hurting elsewhere at the same time.

For instance, perhaps there’s a little twinge in your back every time you also feel the chest pain upon lying on your left side.

dr. polin
Dr. Polin is board certified by the American Board of Internal Medicine, ABIM – cardiovascular disease, ABIM – interventional cardiology and certification board of nuclear cardiology.
Lorra Garrick has been covering medical, fitness and cybersecurity topics for many years, having written thousands of articles for print magazines and websites, including as a ghostwriter. She’s also a former ACE-certified personal trainer.  


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