13 Surprising Reasons You’re Nauseous

When nausea strikes, it’s undeniable. That familiar queasy feeling is a classic symptom of motion sickness and the flu and a common side effect of chemotherapy.

Often there’s a very specific, easy-to-pinpoint cause of nausea, notes Yevgeniy Vaynkof, MD, a family physician at Medical Offices of Manhattan in New York City, like morning sickness or how much you had to drink last night. “However, at times the root cause is not as obvious and requires a thorough investigation,” he says.

So what’s making you green? Here are some possible causes of nausea that you may not have suspected.

Nausea can be a common symptom of anxiety. Here’s what happens: When you’re in the throes of, say, a panic attack, your body shifts into “fight-or-flight” mode. Adrenaline is pumped into your bloodstream, preparing you to take on the perceived enemy or mount a speedy escape.

In the meantime, bodily functions like digestion come to a virtual standstill, which leads to the accumulation of certain toxins in the body, Dr. Vaynkof explains. Eventually, chemical signals reach your brain and spark the sensation of nausea, he says.

Nausea, vomiting, and abdominal pain? Classic signs of a stomach bug. But these same symptoms can be a red flag for a serious complication of type 1 diabetes, says endocrinologist Elizabeth Holt, MD, assistant consulting professor of medicine at Duke University School of Medicine. Diabetic ketoacidosis occurs when energy-starved cells (which don’t get the sugar they need when the body doesn’t produce enough insulin) begin burning fat for fuel, causing high levels of chemicals called ketones to build up in urine and blood. People start to feel bad and get nauseated when they go into ketoacidosis, Dr. Holt says.

The condition can lead to coma or death, especially in people who don’t know they have diabetes or don’t recognize the warning signs, such as extreme thirst and frequent urination.

This hormonal disorder means your adrenal glands, which are right above your kidneys, can’t produce high enough amounts of certain hormones. One cause of adrenal insufficiency is Addison’s disease, an autoimmune disease that damages the adrenals and limits their production of cortisol, a vital hormone for growth, metabolism, and other functions.

How do you know if your adrenals aren’t working properly? “The classic symptoms are nausea, vomiting, diarrhea, weight loss, and, if it continues, your blood pressure goes down so much you go into shock,” Dr. Holt says. People with adrenal insufficiency who experience these symptoms should seek immediate medical attention; without treatment, the condition can be deadly.

Beware of nausea or a sick feeling in your stomach–even if you don’t have chest pain. It can mean you’re having a heart attack.

Women are more likely to report these less typical cardiac symptoms than men, says Amnon Beniaminovitz, MD, a cardiologist at Manhattan Cardiology in New York City. He’s had patients who present with acid reflux-like symptoms who’ve actually suffered heart attacks, so it’s really important to get checked out.

“Sometimes the pain of heart attack is described as stomach pain, or pain in the middle of the upper abdomen,” he says. Rather than a sharp, stabbing pain, it can feel more like “discomfort or heaviness” or even indigestion.

Heartburn is the hallmark of acid reflux and GERD (gastroesophageal reflux disease). But fiery pain in your chest or abdomen isn’t the only symptom. When stomach acid or stomach contents churn back into the esophagus, some people experience nausea.

Dr. Beniaminovitz recalls a 26-year-old male who came in with nausea and discomfort, symptoms that can signal a possible heart attack. After a thorough workup to rule out a cardiac cause, the young man’s problem was easy remedied with over-the-counter proton pump inhibitors, he says.

Nausea is among the unpleasant symptoms that accompany gastroparesis, a potentially debilitating digestive disorder. For various reasons (sometimes a complication of diabetes), the movement of food from the stomach to small intestine slows or stops altogether.

“Food sits around in your stomach–warm and dark and moist–and ferments,” says Virginia Beach-based gastroenterologist Patricia Raymond, MD, assistant professor of clinical internal medicine at Eastern Virginia Medical School.

You’d likely know if you swallowed something you weren’t supposed to. But then again, you might not: Adults have been known to accidentally ingest stray fish bones from a salmon dinner or a wire barbecue brush bristle that gets stuck to the grill and embedded in a burger. That foreign body in your stomach can lead to nausea, vomiting, and abdominal pain.

More common, however, is intentional swallowing of non-food items, as a result of a psychiatric condition or substance abuse disorder.

Sudden right-side abdominal pain after a meal of greasy or fatty food is a classic description of a gallbladder attack. The pain usually strikes when hard particles, called gallstones, block ducts that carry bile (which aids digestion). Occasionally, though, people with gallbladder problems just have nausea, Dr. Raymond says.

Whether it’s pain or nausea that’s bothering you, don’t assume you’re “out of the woods” if stones don’t show up on an ultrasound, she adds. Other imaging tests can assess gallbladder function, which may reveal trouble with your bile-storing organ. Sometimes, she says, “we discover that it’s inflamed and thick and ugly.” If gallstones aren’t causing that queasiness, inflammation, infection, excessive alcohol consumption, or even a tumor may be to blame.

This scary syndrome, which is more common among children but affects adults too, causes sudden, repeated attacks of severe nausea and vomiting for no apparent reason. A single episode can last for hours or days.

“Mild nausea is not the way you would describe these people,” Dr. Raymond says. “They’re just laid low by this.”

While the cause is unclear, research reveals an association between cyclical vomiting syndrome and migraines–even simply a family history of the intense headaches. Patients are typically treated with migraine medicine.

Pale and nauseous at the sight of blood? That uneasy feeling–and subsequent fainting–is vasovagal syncope, a brief loss of consciousness also called “passing out.”

Triggers such as pain, anxiety, prolonged standing, and straining to have a bowel movement can all lead to a sudden drop in heart rate and blood pressure. Before blacking out, people can feel lightheaded and queasy, and they may have heart palpitations. Other symptoms include a clammy or sweaty feeling, ringing in the ears, or blurred or tunnel vision.

This odd cascade of symptoms occurs when some trigger stimulates the vagus nerve, which controls involuntary body functions. “When it is over-stimulated, it can cause the feeling of nausea,” Dr. Beniaminovitz says.

Plenty of prescription and over-the-counter medications carry nausea as a side effect. These include oral bisphosphonates for osteoporosis and injectable diabetes medicines that control blood sugar by slowing digestion. Some blood pressure drugs, antidepressants, and antibiotics can also cause nausea. Talk to the prescribing doctor if you’re on any of these medications and experience queasiness.

Even common pain relievers like aspirin, ibuprofen, and naproxen, known as nonsteroidal anti-inflammatory drugs (NSAIDs), can cause nausea (as well as a risk of erosion of the lining of the stomach and bleeding.)

“In the time that they sit on the surface of the stomach, which is anywhere between a half-hour and an hour, they can cause significant irritation,” says doctor of pharmacy Patrick Meek, associate professor at the Albany College of Pharmacy and Health Sciences. Take them with food to avoid nausea, or look for “enteric-coated” versions that help protect the stomach.

Certain vitamins and supplements should also be taken with food to avoid queasiness. Iron and vitamin C in particular can upset your stomach. “They have a local irritating effect just because of the formulations, but as soon as they pass the stomach, those symptoms tend to subside,” Meek says.