Upper Back Pain on the Left: Muscle or Heart?

Upper back pain on the left is most often a muscle or joint problem, and it is rarely the heart. Still, the left side is where the heart sits, so it is worth knowing which signs call for help before anything else. This page starts there, then looks at the everyday habits that load the left side. It sits alongside medical care and cannot tell you what is causing your pain.

Signs to act on first with upper back pain on the left

Please read this part before the rest, even if your pain feels like an ordinary ache. Call emergency services, rather than waiting to see how it goes, if the pain comes with any of these:

• pressure, squeezing or heaviness in the chest
• pain that spreads into the left arm, the neck or the jaw
• shortness of breath
• a cold sweat
• nausea, or a sudden wave of faintness
• sudden weakness or numbness, difficulty speaking or seeing, or losing control of your bladder or bowels

Women and people with diabetes may notice quieter signs. These can include unusual tiredness, a vague sense of being unwell, or back pain on its own. So a strange, new pain in the upper left back, with no clear reason for it, is worth taking seriously at any age.

Two more situations need the same quick response. One is a sudden, severe, tearing pain in the chest or back. The other is pain that sharpens when you breathe in, together with breathlessness. Either can point to a problem with a large blood vessel or with the lung.

None of this is meant to alarm you. Most people with this pain are fine. But these signs are the reason to act first and ask questions afterwards.

Why the muscles on the left often get the blame

When no warning sign is present, the cause is usually ordinary. In one review of chest pain seen by family doctors, problems in the muscles, joints and cartilage of the chest wall made up roughly a quarter to a half of cases (Haasenritter et al., 2015). That review counted chest pain, not back pain, so it gives no figure for your back. It does show how often an ache near the heart turns out to come from muscles and joints.

The left side picks up its own patterns from the way you live. Notice whether any of these sound familiar:

• Carrying on the left. A bag, a child or a laptop case on one shoulder keeps the muscles beside the left shoulder blade holding on all day.
• Phone habits. Holding a phone against the left ear, or looking down at it in the left hand, tilts the head and shoulder to that side for long stretches.
• Your sleeping shape. Lying on the left with the arm tucked under you, or with the head propped awkwardly, can leave the area tight on waking.
• A turned desk or screen. If your monitor sits off to the left, you twist a little toward it many times a day.
• The work of the other side. If your right hand does most of the mouse work, the left arm often props you up, rests on a desk edge or braces the body.

None of this is a fault. It is simply a body doing one job for a long time. For the wider picture of how this holding builds, see the Feldypedia guide to neck and shoulder tension.

How a muscle pattern feels, and what it cannot tell you

A muscle or joint often has a recognisable pattern. The pain may change when you turn, reach or shift position. The spot may feel tender when you press on it. It may ease a little after you move your arm, or ache more at the end of a long day at the desk.

Keep one caution in mind. A pattern like this does not rule out the heart. Some people with a heart problem press on a sore spot and find it tender too. So use these clues to understand your habits, not to decide that you are safe. If any warning sign from the top of the page is present, it comes first.

Other causes a clinician may look for

Some causes sit outside the muscles, and a doctor is the right person to sort them out. For the wider list, see our page on the causes of upper back pain.

• Shingles. This starts as burning, tingling or sharp pain in a band on one side of the body, often a day or more before a blistering rash shows up.
• The lung. Irritation of the lung or its lining can cause pain that changes with breathing.
• The spleen. It sits under the lower left ribs, and trouble there can be felt in the upper left belly or the left shoulder.
• The pancreas. Pain from the upper belly can travel through to the back. If this pain is severe, go to an emergency department.

You do not need to work out which one it is. What matters is noticing that the pain does not behave like a muscle, then telling your doctor. Also see a doctor promptly after a fall or a blow, or if the pain comes with fever, wakes you at night, or arrives with weight loss you cannot explain.

Gentle ways to notice what loads your left side

If a clinician has no concern, small observations can be a good place to begin. Over a normal day, simply notice which task asks your left side to hold. It might be the bag strap, the phone, the turned screen or the way you sit on the sofa. You can also try these:

• Change position every half hour or so.
• Let your left arm rest on something, so the shoulder does not carry its weight.
• Turn your whole chair, rather than your upper back, toward the screen.
• Breathe slowly, and imagine the back of your left ribs widening a little.

In the Feldenkrais Method®, the shoulder blade, ribs and spine are not treated as separate parts. They move together, and when one holds, the others share the load. By moving slowly and sensing the difference, many people notice where they hold on without meaning to. If the ache travels up toward the neck, you may like Feldenkrais for neck tension. For a related page on a sore, worked muscle, see upper back strain, and for the same question on the other side, read pain in the upper right back or behind right shoulder blade pain. If you would like gentle guidance, Feldy offers short audio lessons you can try free for seven days.

The one thing to take away is simple. Notice which everyday task loads your left side, and if any warning sign comes with the pain, get help first.

Common Questions about upper back pain on the left (FAQ)

When should upper back pain on the left worry me?

Call emergency services if the pain comes with chest pressure, pain spreading to the arm, neck or jaw, breathlessness, a cold sweat, nausea or faintness. Do the same for sudden tearing pain, sudden weakness, or pain that sharpens with each breath alongside breathlessness. For milder pain that stays, grows or has no clear pattern, book a visit with your doctor.

Can a heart problem cause pain only in my upper left back?

Yes, it can. Heart pain is often felt in the chest, but it can show up in the back, arm, neck or jaw, and sometimes it is the only sign. Women and people with diabetes more often notice subtler signs, such as unusual tiredness or back pain alone. When in doubt, act as though it is urgent and call emergency services.

How can I tell if upper left back pain is a muscle?

A muscle pattern tends to change with movement or position, and the spot is often tender when you press it. It may ease when you shift your arm or change how you sit. This is only a clue. A muscle pattern does not rule out the heart, so the warning signs always come first.

How long does a strained upper back muscle on the left take to settle?

Many people notice muscular aches easing over days to a few weeks, especially once the habit that loaded the area starts to change. If the pain lasts longer, keeps returning or slowly grows, have a clinician look at it.

How often should I move gently when my left upper back aches?

Little and often usually suits this area. A minute or two every hour, to change position and notice your left arm, often feels gentler than one long session. Keep every movement comfortable, and pause if the pain sharpens or any warning sign appears.

How is left sided pain different from pain on the right?

The muscles behave in a similar way on both sides, so the everyday causes look alike. What differs is what sits nearby. Most of the heart and the spleen lie on the left, while the gallbladder and most of the liver are on the right. That is one reason to think of the heart first with left sided pain, though heart pain can appear on either side.

Can shingles cause upper back pain on one side?

Yes. Shingles often starts as burning, tingling or sharp pain in a band on one side of the body, a day or more before a rash with blisters appears. If you notice a band like this, see your doctor soon, because early treatment can help.