A fever is generally a temperature of 100.4°F (38°C) or higher. A reading just below that usually isn’t considered a true fever, though everyone’s baseline varies a little.
How you measure matters:
- Adults and older children: an oral temperature is usually fine.
- Infants: a rectal temperature is generally the most accurate.
- Always note the reading, the type of thermometer and the time you took it. Your provider will want those details.
Why Would You Have a Fever and No Other Symptoms?
Fever is a sign that your immune system is responding to something. It is not a disease on its own, and it can show up before other symptoms do. Common reasons include:
Early viral infection
Flu, COVID-19, RSV and other viruses often start with a fever and chills before the cough, congestion or sore throat appears. If a fever arrives alone, watch for new symptoms over the next day or two.
Urinary tract infection (UTI)
A UTI can cause a fever without much else, especially in young children and older adults, who may not describe burning or urgency. A urine test can check for it quickly.
A reaction to a vaccine
A mild fever after a vaccine is common and usually passes within a day or two. If it’s high or lasts longer, get it checked.
A medication reaction
Some medicines can cause a fever. Tell your provider about anything new you’ve started, including supplements.
Heat illness
In Las Vegas, long periods outdoors in extreme heat can raise body temperature. This is different from an infection-driven fever and can become an emergency. A very high body temperature with confusion, dizziness or hot, dry skin needs 911, not a wait-and-see approach.
An early bacterial infection
Strep throat, sinus infections, ear infections and pneumonia can all start with few clues. A hands-on exam helps find the source.
Other causes
Inflammatory and autoimmune conditions, and less commonly other illnesses, can cause fever. More than 200 conditions can cause a fever without an obvious source, which is why a fever that lasts or keeps returning deserves an exam instead of more guessing.
Teething and fever: teething may cause a slight rise in temperature, but a true fever in a baby shouldn’t be written off as teething.
When to Get Care for a Fever Without Symptoms (By Age)
| Who | When to get care |
|---|---|
| Baby under 3 months | Any fever of 100.4°F (38°C) or higher is an emergency. Go to the ER or call your pediatrician right away, even if the baby seems fine. |
| Baby 3 to 6 months | Call your pediatrician the same day for a fever of 100.4°F or higher. Go to the ER if the baby is very sleepy, hard to wake or unusually irritable. |
| Baby or toddler 7 to 24 months | A rectal temperature above 102°F (38.9°C) that lasts more than a day with no other symptoms should be seen by a provider. Go sooner if other symptoms appear. |
| Older children | Behavior matters more than the number. Get care if the fever lasts more than 3 days, rises above 103°F (39.4°C), or your child is unusually sleepy, in pain, not drinking, or “just not acting right.” |
| Adults | Contact a provider for a fever of 103°F (39.4°C) or higher, or one that lasts more than 3 days. Go right away with any red flag below. |
| Higher-risk groups | Adults 65 and older, people who are pregnant, and people with chronic conditions such as diabetes, heart, lung or kidney disease or a weakened immune system should get care sooner. Fever after recent surgery or during chemotherapy is a reason to go to the ER. |
These are general guidelines, not a diagnosis. If you’re worried, trust that instinct and get seen.
Home, Urgent Care or ER? A Quick Decision Guide
| Your situation | Where to go |
|---|---|
| Mild fever, alert, drinking fluids, under 3 days, otherwise healthy | Home care and close monitoring |
| Fever lasting more than 3 days, or coming and going | Urgent care or primary care |
| Fever of 103°F (39.4°C) or higher, but you’re alert, breathing comfortably and drinking | Urgent care promptly. Go to the ER if it won’t come down or you develop red flags. |
| Fever plus urinary symptoms, sore throat, ear pain, cough or body aches | Urgent care for an exam and testing |
| Fever after travel, new medication or a vaccine that isn’t improving | Urgent care or primary care |
| Child over 3 months with a fever that isn’t improving or worries you | Urgent care or your pediatrician |
| Baby under 3 months with any fever | ER |
| Any red flag listed below | ER or 911 |
Go to the ER or Call 911 If a Fever Comes With:
- Confusion, extreme drowsiness or difficulty waking up
- A stiff neck, severe headache or sensitivity to light
- A rash that doesn’t fade when pressed
- Trouble breathing or chest pain
- A seizure
- Persistent vomiting, or signs of dehydration such as dizziness, very dry mouth or dark urine
- Severe abdominal pain
- Fainting or a very fast heart rate
- A very high body temperature after heat exposure
- A fever while on chemotherapy or with a weakened immune system
What Happens at an Urgent Care Visit for Fever?
At Sahara West Urgent Care, a provider will ask about your symptoms, when the fever started, your medical history and recent exposures, then examine you. Depending on what the exam suggests, they may order tests such as flu, RSV or strep tests, urine testing for a UTI, blood work or an X-ray. Learn more about our urgent care services and on-site X-ray availability.
If a cause is found and can appropriately be treated in urgent care, your provider can discuss treatment. If your symptoms need emergency care, we’ll tell you so you don’t lose time.
Want to know how long respiratory test results take? See how long flu test results take, how accurate rapid flu tests are, and when to get tested for COVID-19 if you have symptoms.
How to Care for a Fever at Home While You Decide
- Rest and let your body fight the infection.
- Drink plenty of fluids, such as water or oral rehydration drinks. Avoid alcohol.
- Dress lightly and keep the room comfortably cool.
- Use fever reducers carefully. Over-the-counter medicines can make you more comfortable, but follow the label, and ask a pharmacist or doctor about dosing for children. Ask a doctor before giving any fever medicine to a baby.
- Never give aspirin to children or teenagers. It’s linked to a rare but serious condition called Reye’s syndrome.
- Keep a log of temperatures, symptoms and medicines.
What to Track and Tell Your Provider
Having these details ready helps your provider find the cause faster:
- Temperature readings, how you took them, and when
- When the fever started and whether it has come and gone
- New symptoms that appeared later
- How much you or your child is drinking, and how often you’re urinating
- Medicines taken, including fever reducers and the times
- Recent vaccines, new medications, travel, heat exposure or sick contacts
- Chronic conditions, pregnancy, or anything affecting your immune system
Visiting Las Vegas or Living Nearby
Sahara West Urgent Care is at 6125 West Sahara Avenue, Las Vegas, NV 89146, convenient for patients in Las Vegas, Spring Valley, Summerlin, Enterprise, Winchester, Paradise, Henderson and The Strip. Fever after travel or a few days outdoors in the heat is one more reason to get an exam, because the cause isn’t always obvious.
Hours: Monday to Friday 9:00 AM to 8:00 PM · Saturday 9:00 AM to 3:00 PM · Sunday closed. If you need emergency care when we’re closed, go to the nearest ER.
We accept a wide range of insurance plans, and self-pay patients can call (702) 248-0554 for pricing. Ask about our membership plans. For ongoing care and follow-up, our primary care team can help.
FAQs
Can you have a fever with no other symptoms?
Yes. A fever can be the first sign of an infection before other symptoms develop. It can also be caused by a vaccine, a medication or heat. If it lasts more than a few days or keeps returning, get it checked.
What causes a fever with no other symptoms?
Common causes include an early viral infection, a UTI, a reaction to a vaccine or medication, heat illness, and early bacterial infections such as strep or a sinus or ear infection. Less often, inflammatory or other conditions are responsible.
Is a fever with no other symptoms serious?
Usually not, especially in a healthy adult who feels fairly well. It becomes more serious in babies under 3 months, in higher-risk groups, when it’s very high, when it lasts more than 3 days, or when red flags appear.
How long can you wait before seeing a doctor for a fever?
For a healthy adult, a day or two of monitoring is reasonable if you’re otherwise okay. See a provider if the fever lasts more than 3 days, reaches 103°F (39.4°C) or higher, or keeps coming back. Babies and higher-risk people should be seen much sooner.
What temperature is too high?
There is no single number. Fever is 100.4°F (38°C) or higher. In adults, 103°F (39.4°C) or higher needs prompt attention. In babies under 3 months, any fever needs emergency care. Symptoms and behavior matter as much as the reading.
Should I go to urgent care or the ER for a fever?
Urgent care is appropriate for many fevers when you’re alert, breathing comfortably and drinking fluids. Go to the ER for fever with confusion, a stiff neck, trouble breathing, a seizure, a non-fading rash, severe pain or persistent vomiting, or for any fever in a baby under 3 months.
What should I do about a fever with no symptoms in a baby or toddler?
For a baby under 3 months, go to the ER or call your pediatrician immediately. For a baby or toddler between 7 and 24 months, a rectal temperature above 102°F (38.9°C) lasting more than a day with no other symptoms should be seen by a provider. Call sooner if the child is unusually sleepy, irritable or not drinking.
Can a vaccine cause a fever with no other symptoms?
Yes. A mild fever after a vaccine is common and usually resolves within a day or two. If it’s high, lasts longer, or comes with other worrying symptoms, get it checked.
Do I need an appointment at Sahara West for a fever?
No. Walk-ins are welcome during regular hours, and you can book ahead if you prefer.
Don’t Guess. Get Answers Today.
If a fever won’t go away, keeps coming back, or you’re not sure how worried to be, an exam can point to the cause and the next step.
Walk in to Sahara West Urgent Care at 6125 West Sahara Avenue, Las Vegas, NV 89146, call (702) 248-0554, or book an appointment online. You can also contact us with questions.
This article is for general information and isn’t medical advice. If you think you or someone else is having an emergency, call 911 or go to the nearest emergency room.
