When you wake up in the middle of the night with an alarming symptom—maybe it's a high fever or splitting headache—it's hard to know whether to rush to the emergency room or not. You don't want to overact, but you definitely don't want to underreact either. So how do you know when that stomach pain needs to be treated ASAP or if that numb feeling can wait until morning to deal with? We spoke to Ryan Stanton, MD, a board certified emergency physician and spokesman for the American College of Emergency Physicians to find out.

Headache
While you may be used to the occasional headache from stress or one too many drinks, certain types of headaches can be cause for more concern. The three most common—and not dangerous—types of headaches are tension, cluster, and migraines, but "there are a couple of characteristics we look for as emergency doctors that tip us off that a headache is more than the average headache," explains Stanton.

Head to the ER if…the pain is intense and sudden. "Is it the worst headache of your life? Did it come on suddenly like you were struck by lightning or hit in the head with a hammer?" says Stanton. "These are the two major questions we will ask to gauge the risk for a potentially deadly cause of headache known as subarachnoid hemorrhage." A headache is also worrisome if it is accompanied by a fever, neck pain, or stiffness and a rash, which could signal meningitis.

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Abdominal Pain

From tummy aches to belly bloat, abdominal pain is the number one non-injury reason for adult emergency room visits, according to the National Hospital Ambulatory Medical Care Survey. The pain can be caused by a number of factors from gas or a pulled muscle to the stomach flu or more serious conditions like appendicitis or urinary tract infections. 

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Head to the ER if… you're experiencing intense localized pain, especially in the right lower part of your abdomen or your right upper region, explains Stanton, as this could hint at an issue with your appendix or gallbladder that may require immediate surgery. Other concerning symptoms are abdominal pain accompanied by an inability to keep down any food or fluids, blood in the stool, or a severe and sudden onset of the pain.

Chest Pain

With heart attacks as the number one killer for both men and women, it's no surprise that sudden chest pain can be scary and is one of the leading causes of emergency room visits for adults. "Heart attacks are at the top of the list due to their frequency and potential risk," says Stanton. 

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Head to the ER if… you are experiencing chest pain along with shortness of breath, decreased activity tolerance, sweating, or pain that radiates to the neck, jaw, or arms—especially if your age or family history puts you at a higher risk for heart attacks. "This is not a time for the walk-in or urgent care clinic," says Stanton. "They will just take a look and send you to the ER since they don't have the ability to deal with cardiac-related issues." (Read Heal Your Heart today to learn how to cut your heart attack risk by 50%.)

Infection 
Infection can run the spectrum from a simple infected skin wound to serious forms such as kidney infections. The vast majority of infections are viral, which means they won't respond to antibiotics and can be treated at home with over-the-counter symptom management until the virus passes. The key then is to look at the severity of the symptoms. "The more severe infections are sepsis (infection throughout the body), pneumonia, meningitis, and infections in people who have weakened immune systems," says Stanton.

Head to the ER…based on the severity of your symptoms. "You want to show up at the ER if there are any concerns, such as confusion, lethargy, low blood pressure, or inability to tolerate any oral fluids," says Stanton. "These may suggest a more sinister infection or may just need a little emergency room TLC, such as medications to help with symptom management, fluids, or possibly antibiotics, to turn the corner."

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Blood in your stool or urine
Blood shouldn't ever be found in your stool or urine, so even if your symptoms don't require a trip to the ER, it's important to make an appointment with your physician as soon as possible to determine the source and decide on a treatment plan. "Blood in the urine is usually caused by some kind of infection such as a urinary tract or kidney infection or kidney stones," says Stanton. "When it comes to stool, it's often benign, but it can be the sign of something very dangerous." The number one cause is hemorrhoids followed by fissures, infections, inflammation, ulcers, or cancer. If you have a little blood with no other symptoms, make an appointment to talk with your doctor. 

Head to the ER if… you have blood in your stool or urine with other symptoms such as a fever, rash or fatigue, large amounts of blood, intense pain, or any evidence of a blockage.

Difficulty Breathing

"Shortness of breath is one of the most common emergency department presentations," says Stanton. The most common causes are asthma, Chronic Obstructive Pulmonary Disease (COPD) from smoking or infections such as pneumonia. When it comes to shortness of breath, it's pretty straightforward, says Stanton. "If you can't breath, get to the ER."

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Head to the ER if…always.

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Cuts, Bumps & Falls
Whether it's a knife accident chopping veggies for dinner or a misstep off the deck stairs, many cuts, bumps, and bruises can be handled at home with icing or home first aid kit supplies.

Head to the ER if…what's supposed to be on the inside is on the outside, or what's supposed to be on the outside is on the inside, says Stanton. If you can see muscle, tendons, or bone, it requires more than just a BandAid. "It's important to get these addressed because they are fraught with potential secondary complications from infection to loss of function and ischemia [reduced blood flow]," warns Stanton. 

Vomiting
While not pleasant, vomiting is a common symptom that can be caused by a number of conditions, most often viral gastroenteritis ("stomach flu") or food poisoning. Usually vomiting can be managed with home care and a check-in with your primary care doctor. (But before you waste time in your doc's waiting room, be sure to learn these 10 Secrets Every Doctor's Receptionist Knows.)

Head to the ER if…there is blood in the vomit, significant stomach pain, or dark green bilious vomit which could suggest bowel obstruction. Another important factor with vomiting is dehydration. "If you are unable to keep anything down, you will need to get medication or treatments to help you stay hydrated," explains Stanton. "Young children can become dehydrated rather quickly, but most healthy adults can go several days before significant dehydration becomes an issue."

Fever

"Rarely is a fever anything other than an indication that you are ill," Stanton explains. It's actually a healthy sign that your body is responding to an infection. The concern then is not with the fever itself, but with what infection is causing the fever. Don't hesitate to treat it with over-the-counter medicines such as ibuprofen. 

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Head to the ER if…a fever is accompanied by extreme lethargy or there are other symptoms of infection present. Most concerning to Stanton are "fevers in kids with lethargy, fevers in adults with altered mental status, and fevers with headache and neck pain."

Loss Of Function 

Numbness in your legs, slack facial muscles, a loss of bowel control—if a certain body part or body function stops working suddenly or over time, it's worth finding out why. 

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Head to the ER…always, recommends Stanton. "Whether it is due to a trauma or just develops over time, any loss of function requires immediate evaluation." The two most common causes are physical trauma and stroke, both of which are serious and require medical attention. "When something is not working, don't try to 'sleep it off'," advises Stanton. "If it doesn't work, there is a reason and we need to see if we can diagnose, reverse, or prevent ongoing problems."

The bottom line for any symptom: If you truly can't decide what to do, it's better to be safe than sorry. "Any time you have a concern or emergency, it's always better to get checked than to wait until the problem escalates," recommends Stanton.