SHIVERING AND FEELING CHILLY are common cold and flu symptoms that usually, accompany a fever. But sometimes, you might start feeling cold and shaky out of nowhere, when you’re not sick and don’t have a fever.
“It’s really common, and there are a number of reasons why it happens,” says Jeffrey Quinlan, M.D., chair and department executive officer of the Department of Family Medicine at the University of Iowa Carver College of Medicine.
When you get the chills and don’t have a fever, it might be a sign of a health problem that needs to be looked into, especially when it happens frequently, says Hannah Cohan, N.P., a board-certified nurse practitioner with Medical Offices of Manhattan.
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“There could be a link to infections, long-term illnesses, or problems with the immune system,” she explains. In other instances, having chills without a fever isn’t much to worry about—maybe you’re just cold-natured or you spent too much time outside in the cold.
Our bodies are equipped with intricate systems that tightly regulate our body temperature, keeping it in a healthy zone, which is about 97 to 99 degrees Fahrenheit. When something, whether it’s minor or severe, interferes with that process, it can leave you trembling or feeling like you suddenly stepped into a walk-in freezer.
“If you’re having recurrent chills, in particular, and there’s no other real reason for them, that’s a reason to see your physician, because it could be a number of things,” says Dr. Quinlan. Your doctor may run some tests to rule out any major health problems.
Here are a few health concerns or circumstances that can cause chills without a fever:
1. Being in a Cold Environment
It may sound obvious, but the most common reason for chills with no fever is that you’re actually cold. Maybe you didn’t realize your air conditioning kicked on so high, or you stayed outside for too long on a freezing day.
Here’s what happens: Your skin has special receptors that sense the cold and send messages to your brain telling you it’s time to warm up. As a result, you might adjust your behavior by moving to a warmer environment or layering on a blanket or more clothes, says Andrej A. Romanovsky, M.D., Ph.D., an Arizona State University professor and researcher who studies body temperature regulation.
However, if you stay in a cold environment, your blood vessels can start to constrict to limit heat loss. Next, you might start shivering. Your muscles are contracting to increase your body’s heat production and raise your temperature.
“Shivering is very expensive because it involves burning energy,” says Dr. Romanovsky. “These dis-coordinated, high-frequency movements interfere with your performance, and so shivering is turned on usually relatively late during cold exposure.” (Receptors in our skin also respond to certain chemicals by making us feel chilly, he says. That’s how a toothpaste or muscle rub with menthol can give you goosebumps.)
2. Cold-Weather Workouts
A workout in cold temperatures can also induce chills quickly, especially when you push hard. Active muscles produce heat, but once you stop exercising, that heat dissipates and can ultimately lower your body temperature, says Dr. Quinlan. You might even develop muscle cramps, nausea, or vomiting as a result.
What can you do? Warm up and dry off, if necessary. Wet clothing can send you into the shiver zone especially fast.
“As your body heats up, your natural body heat will cause evaporation of the water in your clothes, and so that just takes more heat from your body and makes you more likely to have more chills if your clothes are wet versus dry,” says Dr. Quinlan.
Dehydration happens when your body loses too many fluids, from sweating, vomiting, or diarrhea. You can also lose water if you go out running on a hot day or just spend time outdoors when the temperatures rise. In extreme cases, Cohan says dehydration can sometimes cause your body temperature to drop, which might make you feel cold, intolerant to heat, or get the chills. Essentially, dehydration may lead to hyperthermia because overheating can alter your body’s normal temperature.
4. Viral Infections
Infections can cause chills with or without a fever. A virus can act directly on your nervous system and indirectly influence it through protein molecules that tell neural cells that your body temperature is too low, says Dr. Romanovsky. The result: You feel cold, and your body kicks in with shivering and other natural mechanisms to heat you up.
“The infection might only be in one part of the body and not affect the core temperature enough to cause a fever,” Cohan says. “Other things, like how sensitive each person is to temperature, the type of virus, and the stage of an illness, can also affect whether or not a person has a fever.”
Although fever is a common symptom of Covid-19, some people infected with the virus report chills without a fever. So, if you have chills along with other common Covid symptoms, such as a sore throat, runny nose, nausea and vomiting, fatigue, cough, or diarrhea, it’s worth taking a Covid test, says Dr. Quinlan.
5. Bacterial Infections
If a bacterial infection goes untreated for too long, it can make you really sick. Often, this results in a fever, but chills sans fever have been reported in people with a range of infections, too. Typically, chills won’t be your only symptom of a bacterial infection, says Dr. Quinlan.
One potentially life-threatening example is meningitis, which can cause chills with or without a fever, along with symptoms like a stiff neck, sensitivity to light and sound, and lethargy. Those symptoms warrant a trip to the emergency department, Dr. Quinlan says.
Malaria is another example. This condition can make people feel chilly and shivering one minute and hot and sweaty the next. Consult a doctor if you’ve recently traveled to a destination where malaria is common—the CDC website maintains a list.
Sometimes, people with Lyme disease also report chills with no fever, says Dr. Quinlan. If you have a history of a tick bite, especially if you’ve seen a bullseye-shaped rash at the site of the bite, contact your doctor.
With bacterial infections, prompt treatment with the right antibiotic is critical. If you suspect this is the cause of your chills, see a healthcare provider right away.
6. Anxiety or Fear
That surge of adrenaline that happens when you’re scared or super stressed? It can make you feel cold or give you the chills, Cohan says.
That’s because adrenergic nerves are part of a loop of chemical and electrical signals that temporarily activate your body’s shivering response when you experience anxiety or fear, Dr. Romanovsky. Through similar pathways, strong positive feelings can also give you chills.
7. Panic Attack
Fear or anxiety that leads to a panic attack can cause shivering or chills. Cohan says feeling anxious or scared activates your body’s fight-or-flight response, triggering the release of hormones like adrenaline.
The stress hormones can narrow blood vessels, sending blood to areas of the body that need it most and causing the temperature of your extremities to drop, she explains. “This change in the body can cause shaking or chills, among other things.”
Also, during a panic attack, your breathing might become shallow or quick, throwing off the body’s balance of oxygen and carbon dioxide, making the heart beat faster, and this might make you sweat or give you chills, Cohan says.
8. Low Blood Sugar
Low blood sugar, or hypoglycemia, can make you feel cold and shaky. “If your body doesn’t have enough sugar, it is going to look for ways to try to get more energy and activate things,” says Dr. Quinlan.
One of those things it activates is the sympathetic nervous system, resulting in symptoms like chills, sweating, heart palpitations, and blurred vision. Your primary care doctor can check your blood sugar and help you determine what’s up.
9. Blood Pressure Changes
Chills might happen with a sudden blood pressure drop, Cohan says. When your blood pressure gets too low, your organs aren’t getting enough oxygen and nutrients, which can lead to shock, according to the National Heart, Lung, and Blood Institute. Signs of shock include cold, sweaty skin, as well as rapid breathing and a weak, rapid pulse. Call 911 if you notice signs of shock, as it needs immediate medical attention.
“Your thyroid hormone is what’s really responsible for regulating your metabolism in your body, and ultimately, your metabolism helps control how cold or how warm you feel,” says Dr. Quinlan. In hypothyroidism, your thyroid gland is underactive, and your metabolism slows down, sometimes leaving you with chills.
Other common symptoms include tiredness, weight gain, constipation, dry skin and hair, and a slowed heart rate, says Dr. Quinlan. Your primary care doctor can order a blood test to check your thyroid hormone levels.
If you’re anemic, you aren’t producing enough red blood cells, and as a result, your body isn’t moving around as much oxygen as you need, says Dr. Quinlan.
You can also be short on iron and other important electrolytes. As a result, your sympathetic nervous system might kick in with shivering to warm you up and give you some energy. Your primary care provider can check for anemia—and prescribe treatment or iron supplements to reverse it.
Leukemia, a cancer of the blood-forming cells, can make some people feel chilly, especially at nighttime. The culprit? Overproduction of certain kinds of white blood cells that produce hormones and other factors that mimic or activate your body’s sympathetic nervous system to give you the sensation of chills.
Other common leukemia symptoms include fatigue, frequent infections, shortness of breath, pale skin, unexplained weight loss, pain or tenderness in your bones or joints, pain under your ribs on your left side, swollen lymph nodes, and bruising and bleeding easily, according to the Cleveland Clinic. Blood tests, imaging tests, and biopsies can help your doctor determine whether this is the culprit behind your symptoms.
13. Autoimmune Conditions
Some autoimmune illnesses, such as lupus or Crohn’s disease, can interfere with your body’s temperature control mechanism, Cohan says. So, you might experience chills as an early sign of these conditions. That’s why getting any symptom that seems to appear out of nowhere checked out is crucial.
14. Reactions to Medication
“Chills can frequently be related to medication reactions, and sometimes can be a sign of some pretty serious allergies,” says Dr. Quinlan. “And so if you recently started a new medication and start developing recurrent chills, that’s a reason to talk to your doctor right away.”
Diabetes medications, general anesthesia for surgery, and chemotherapy medications are more likely to cause chills.
Some people experience chills after blood transfusions and certain radiology procedures, too, he says. Drug withdrawal can also cause chills in people who use narcotics or antidepressants chronically and then suddenly stop.
15. Other Medical Conditions
Respiratory illnesses, allergies, and the early stages of sepsis may also cause chills, Cohan says.
But there’s always one more thing to consider with chills—a fever could still be on the horizon.
“At the beginning of a fever, we typically feel cold because our bodies want to increase body temperature,” says Dr. Romanovsky, adding that this can take several minutes, depending on a few factors, including your body size. “Shivering is like turning on the heater, but it takes time for the water in a pot to really become warm.”
When to Worry About Having Chills Without a Fever
Chills that go away quickly on their own likely shouldn’t be concerning. But, if they keep coming back and persist, it’s time to call your doctor, Cohan urges.
Also, if you have any of these symptoms, in addition to chills, seek medical attention:
- Chest discomfort or pain
- Severe fatigue and body aches
- Swelling or hives
- Rapid heart rate
- Change in urine color, odor, or frequency
Julie Stewart is a writer and content strategist whose work has also appeared in Health, and Women’s Health, Everyday Health, Vice, and Shape.
Erica Sweeney is a writer who mostly covers health, wellness and careers. She has written for The New York Times, HuffPost, Teen Vogue, Parade, Money, Business Insider and many more.