When Should I Go to the ER for a Fever?

When you or your child comes down with a fever, it’s natural to be a little worried. Most of the time, you can treat fevers at home and you or your child will feel better in a few days. But how can you know if your fever is a sign of something more serious? Not getting good sleep can make it even harder to decide who is too ill to be at home. Let's review what signs you should look for to know when it's time for a same-day visit to your primary care office or the emergency room (ER).

What is a fever? 

Fever is an elevated body temperature that’s usually related to being sick. Fever is one of your body’s defenses to fight off disease. Your immune system works best when your body temperature is higher than normal. And this is what distinguishes a fever from other forms of elevated body temperature, like hyperthermia. 

Fever is when your body makes your temperature higher. Hyperthermia is when something in the environment causes your temperature to be higher — like sitting inside a hot car in the summer. With hyperthermia, body temperatures can get dangerously high. Thankfully, this isn’t a concern with fever.

Interestingly, medical experts have trouble agreeing on what temperature defines a fever. That’s partly because it’s normal to have variations in body temperature throughout the day. The average normal body temperature is 98.6℉ (37℃), with a range from 97.7℉ to 99.5℉. The CDC defines fever as any temperature over 100.4℉ (38℃). 

When should you go to the hospital for a fever?

The reasons to go to the hospital or ER for a fever vary with age. So we’ll break it down by age group below.

Babies 

Fever is treated a little differently in babies and children in comparison to adults. For babies, especially those 3 months and younger, any fever can be worrisome because newborns have immature immune systems. So medical providers are quick to act when a very young baby has a fever.

While there are many ways to take a temperature, the most accurate method is a rectal measurement. Most medical recommendations regarding fever are based on rectal temperatures. 

If your baby (newborn to 3 months) has a fever, these are reasons to take them to the ER:

• Temperature: Both a high or low temperature are concerning. If your baby has a rectal temperature above 100.4℉ or below 97℉, you should take them to the ER. This is also true if your baby’s skin feels cold to the touch, regardless of their temperature. 

• Poor feeding: Newborns will typically feed every 2 to 3 hours. As a baby’s stomach grows, they’ll be able to eat more each time and may feed less often. Seek medical attention if your baby has a consistent decrease in how they’re feeding (for two or three feedings) or if your baby doesn’twake up to feed. 

• Fewer wet diapers: This often goes hand in hand with poor feeding. Most infants will have a wet diaper with each feed, at least once every 3 to 4 hours. Take note if your baby has a consistent decrease in their number of wet diapers (or those diapers are significantly less wet) or hasn’t had a wet diaper in more than 4 hours. This may be a sign that your child is becoming dehydrated.

• Trouble breathing: This includes noisy or congested breathing. But it could also mean your baby looks like they’re working harder to breathe. You might notice you can see their ribs more prominently with each breath or that they need to take frequent breaks during feeding to breathe. 

• Blue discoloration of the lips or skin: This could be a sign of low oxygen levels, which can happen with respiratory infections and severe non-respiratory infections.

• Green vomit: This can sometimes be a sign of something more serious in the abdomen.

• Change in arousal or activity: Babies sleep a lot. But if you notice your baby is more difficult to arouse or seems less playful or vigorous, this could be a sign for concern.  

• Rash: A healthcare provider should evaluate any new or spontaneous rash.

Children

Toddlers frequently get and spread infections that cause fevers — especially when they start to attend day care and school. Luckily, their immune systems are much stronger at that point. So many of these childhood illnesses will get better in a few days on their own. 

But there are still some reasons to go to the hospital when infants, toddlers, and younger children have a fever. These reasons are similar to the reasons for babies, but with a few differences:

• Temperature: The threshold is a little bit higher for older children, and you don’t need to make a trip to the ER for the number alone — unless their temperature is over 102℉.

• Dehydration: Similar to babies, take note if your child has a significant decrease in eating and drinking or if you see a significant drop in how frequently they’re urinating. 

• Trouble breathing or blue color to lips/skin: Signs of a more serious infection include noisy breathing, wheezing, and increased work of breathing. A lot of times you can notice this when it seems they’re using extra muscles to breathe — like the muscles above their collar bones, between their ribs, or abdominal muscles. 

• Trouble waking up: Usually children have an established routine as they get older. Children will wake and nap at generally the same time each day. Head to the ER if you notice that your toddler is sleeping a lot more than usual, especially in a pattern different from their normal routine.

• Stiff neck: At any age, if you notice that your child doesn’t like to bend their neck to look down or up, go to the emergency room immediately. This could be a sign of meningitis. 

• Certain rashes: Many viruses that are common among kids cause harmless rashes. But examples of more concerning rashes include ones that form large blisters, appear on the palms or soles, look like a bullseye or target, or have small, red or purplish spots that look like tiny bruises underneath the skin (also called “petechiae”).  

Adults 

Adults usually have fewer fevers than kids, and their temperatures don’t usually get as high. Adults also tend to have a better internal sense of when an infection is serious, so fevers don’t set off alarm bells as much as they do in kids. But there are still cases in adults when a fever is a sign of an infection that needs urgent medical care.

You should see your provider or go to the emergency room if you have a fever along with one or more of the following symptoms:

• Severe headache or neck stiffness: Mild headaches are common with fever. But if the headache feels more severe or you’re experiencing significant neck stiffness (particularly when touching your chin to your chest), these could be signs of meningitis. And this infection can be serious. 

• Shortness of breath: Most adults know what a typical cold or respiratory infection feels like. But having trouble breathing or shortness of breath can affect your oxygen levels. This is also true if you notice your lips or fingers appear blue or gray.

• Severe abdominal pain: Some infections inside the abdomen — like appendicitis or diverticulitis — need treatment with special antibiotics or surgery.

• Rashes: The combination of new rash and fever is less common in adults than kids. While many causes of rashes aren’t harmful, a few need attention. And even when the rash is a basic skin infection that you can treat at home, some skin infections also need treatment in the hospital.  

• Lethargy, confusion, or disorientation: Older adults have a higher risk for infections that can take a serious toll on their whole body (sepsis) or cause severe dehydration or organ failure. Often the earliest signs of this include abnormal behavior, excessive tiredness, or mild confusion. 

• Weakness or dizziness: It’s best to get checked out if you’re feeling excessively weak, very dizzy when you stand, or like you can’t get out of bed.