Upper Left Stomach Pain: Common Causes and When to See a Doctor

Clinically reviewed by Dr. Ponlawat Pitsuwan, Physician, Doctor Bangkok. Last reviewed: August 2026

I see three or four patients a week with the same description: a dull ache, a burning, or a sharp jab somewhere under their left ribs. Sometimes it started after som tum the night before. Sometimes it woke them up at 3am for no obvious reason. They Googled it and ended up here, which is the right instinct.

The upper left of your abdomen is a busy area. Your stomach sits there, so does part of your pancreas, your spleen, your left kidney, and the bend in your colon. The pain could be coming from any one of them, or occasionally from somewhere else entirely, like your heart. This article helps you figure out which direction to go.

What Organs Are Behind That Pain?

Most people are surprised by how much sits in this corner of the body. Your stomach is the obvious one and usually the culprit. Behind it is your pancreas. To the upper left is your spleen. Your left kidney sits deeper, toward your back. The splenic flexure, the bend in your large intestine, curves through this same space.

The character of your pain gives clues. A burning sensation after eating points toward your stomach or the junction with your oesophagus. Pain that radiates to your back after a heavy meal raises concern for your pancreas. A dull ache that gets worse when someone presses on your upper left side could involve your spleen.

Common Causes of Left Top of Stomach Pain

Gastritis and Peptic Ulcers

This is the most common thing I see. Gastritis is inflammation of the stomach lining. A peptic ulcer is what happens when that inflammation goes deeper and creates a sore. Both cause burning or gnawing pain in the upper left, often worse on an empty stomach or at night.

H. pylori, the bacteria behind most peptic ulcers, is more common in Southeast Asia than in Europe or North America. Street food in Bangkok is genuinely excellent, but H. pylori exposure is a real consideration. If your pain keeps coming back and you have never been tested for it, that is worth sorting out.

Acid Reflux and GERD

Acid reflux happens when stomach acid moves upward into the oesophagus. GERD is the chronic version. The pain tends to sit high, sometimes behind the breastbone, sometimes spilling into the upper left. It gets worse lying down or after large meals.

I see this a lot in patients who have recently moved to Bangkok and changed their diet significantly. Spicy food, irregular meal times, and the heat all play a role. A hiatal hernia, where part of the stomach pushes up through the diaphragm, can make reflux considerably worse and is a common underlying factor.

Pancreatitis

Pancreatitis means the pancreas is inflamed. The pain is usually severe, starts in the upper abdomen, and bores through to the back. It often comes with nausea and vomiting. Alcohol is a common trigger, and so are gallstones.

Mild pancreatitis can be managed with rest and fluids. Severe pancreatitis is a hospital-level problem. If your pain is that intense and came on suddenly after drinking or a heavy meal, do not wait for it to pass.

Spleen-Related Causes

Your spleen does not usually cause pain unless it is enlarged or injured. An enlarged spleen can develop with infections like glandular fever or malaria, both relevant in Thailand. You may feel a heavy fullness under your left ribs that gets worse when you take a deep breath.

Splenic infarction, where part of the spleen loses its blood supply, is rarer but causes sharp, sudden left upper pain. If pain came on abruptly and is not settling, this is one reason a doctor will want imaging.

Kidney Stones or Kidney Infection

Your left kidney sits behind the other organs in this area. A kidney stone causes waves of cramping pain that radiates from your back or flank around to the front. A kidney infection causes a more constant ache and usually comes with fever and burning when you urinate.

Dehydration is a major factor in stone formation. Bangkok’s heat is no joke, and I see kidney stone cases rise during the hot season among patients who are not drinking enough water.

Gas, Bowel, and Splenic Flexure Syndrome

Trapped gas at the bend of your colon on the left side causes sharp or crampy pain under the left ribs that can feel alarming but is not dangerous. It often follows a large meal or a period of constipation. The pain tends to ease when you pass gas or move your bowels.

Functional dyspepsia, stomach discomfort without a clear structural cause, is also common. It is closely tied to stress, and expats adjusting to a new city, new job, and new food culture are prime candidates.

When Left Top of Stomach Pain Is a Heart Warning

This is the one I do not want you to miss. The heart and the structures around it can send pain to the upper abdomen, including the left side. Pericarditis, inflammation of the sac around the heart, can feel very much like stomach pain. Angina and heart attacks sometimes present as upper abdominal discomfort rather than chest pressure.

The clues that point toward your heart: pain that came on with exertion and eased when you rested, shortness of breath or sweating alongside it, or no link to food at all. These warrant an ECG, not antacids. Doctor Bangkok can run an ECG on-site during your consultation.

Bangkok-Specific Triggers Worth Knowing

Expats and travellers in Bangkok face a specific set of triggers that do not appear in generic health articles. Very spicy Thai food irritates the stomach lining, particularly for digestive systems still adjusting. H. pylori exposure through street food is real. Alcohol, a common feature of Bangkok’s social life, directly triggers both gastritis and pancreatitis.

Bangkok’s heat accelerates dehydration faster than most visitors expect. Dehydration raises the risk of gallstones and kidney stones. Traveller’s stomach, the disruption that comes from a new food environment, can also cause cramping that sits in the upper left. These are not textbook cases. They are the patients I see every week.

Musculoskeletal Causes Patients Overlook

Not every pain in this area comes from an internal organ. Muscle strain from exercise, lifting, or prolonged coughing can cause left upper abdominal pain that mimics something more serious. Costochondritis, inflammation of the cartilage where your ribs meet your sternum, can also send pain to this region.

If the pain is worse when you press directly on the spot, changes with body position, or followed a gym session or a long flight, a musculoskeletal cause is likely. It does not need urgent investigation, but it is easy to confuse with something that does.

Red Flags That Mean Act Now

Some presentations of left top of stomach pain need same-day or emergency assessment. Sudden severe pain that came on in seconds is a red flag. So is pain that radiates to your back, left shoulder, or jaw. Vomiting blood or passing black tarry stools means bleeding somewhere in your gut. Fever above 38 degrees Celsius with abdominal pain suggests infection. Dizziness or feeling faint alongside abdominal pain needs urgent attention.

For life-threatening presentations, go directly to a hospital emergency department. For pain that is worsening, has lasted more than a couple of days, or is making you worried, Doctor Bangkok is open for walk-in consultations and can begin assessment straight away.

How Upper Left Stomach Pain Is Diagnosed

A doctor will start with a physical examination, pressing on your abdomen to locate the pain and check for organ enlargement. Blood tests covering your full blood count, inflammatory markers, and liver and pancreatic enzymes are a common first step. A urine test checks for kidney involvement.

An abdominal ultrasound gives direct images of your spleen, kidneys, gallbladder, and pancreas. It is the most useful early imaging tool for this area. If gastritis or an ulcer is suspected, an upper GI endoscopy may be recommended. Doctor Bangkok runs initial blood work in-clinic and coordinates ultrasound and endoscopy referrals when needed.

What Happens When You Come In

When you come in with left top of stomach pain, I take a proper history first. When did it start, what makes it better or worse, what have you eaten, any recent travel or new medications. That conversation alone narrows the field considerably.

Then I examine you. If the picture warrants it, we take blood and run it in our on-site lab. We can do an ECG the same visit if there is any cardiac concern. If you need imaging, we refer you quickly, usually the same day. You leave with a clear plan, a diagnosis where possible, and treatment started. No referral maze, no waiting weeks for an appointment.