Sometimes the chills are nice, like when they’re caused by a passionate new romance, as described by Ed Sheeran in his hit song titled Thrill, sure. But if you start feeling cold and shivering out of the blue, you might wonder if something is wrong. Sometimes the chills are accompanied by a fever, giving you a major clue that you are sick. Otherwise? You might feel even more confused.

“It’s very common, and there are a number of reasons why it happens,” says Jeffrey Quinlan, MD, FAAFP. Quinlan is chairman and chief executive of the Department of Family Medicine at the University of Iowa Roy J. and Lucille A. Carver College of Medicine.

Our bodies are equipped with complex systems that tightly regulate our body temperature, keeping it within a healthy zone, which is around 97 to 99 degrees Fahrenheit. Many problems, ranging from minor to serious, can make you feel like you’ve suddenly stepped into a walk-in freezer.

“If you have recurring chills, in particular, and there’s no other real reason for it, that’s a reason to see your doctor, as it could be a number of things,” says Dr. Quinlan.

Here are some health conditions or circumstances that can cause chills without a fever.

Being too cold, especially after a cold workout

OK, maybe this one is obvious, but the most common reason for chills without a fever is that you’re actually cold. Maybe you didn’t realize your AC was running so loud or you were pushing too hard during a workout in a cold, humid climate.

Here’s what happens: Your skin has special receptors that detect cold and send messages to your brain to tell you it’s time to warm up. As a result, you can adjust your behavior by moving to a warmer environment or layering a blanket or more clothing, says Andrej A. Romanovsky, MD, Ph.D., FAPS, professor and researcher at Arizona State University who studies body temperature. regulator and CEO and founder of Zharko Pharma. However, if you stay in a cold environment, your blood vessels may start to constrict to limit heat loss. Then you might start shivering. Your muscles contract to increase your body’s heat production and raise your temperature.

“Chills are very expensive because it involves burning energy,” says Dr. Romanovsky. “These disorderly high-frequency movements interfere with your performance, and so the shiver is typically activated relatively late during cold exposure.” (The receptors in our skin also react to certain chemicals by making us feel cold, says Dr. Romanovsky. This is how a menthol toothpaste or muscle rub can give you goosebumps.)

What can you do? Warm up and dry off if necessary. Wet clothes can send you into the chill zone particularly quickly. “As your body heats up, your body’s natural heat causes water from your clothes to evaporate, which simply draws more heat from your body and makes you more likely to have more chills if your clothes are wet or dry,” says Dr Quinlan.

Working out in cold weather can also cause quick chills. The activity of your muscles produces 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.

Viral infections such as Covid-19

Infections can cause chills with or without fever. Infectious viruses (and bacteria, but more on those in a moment) can act directly on your nervous system and influence it indirectly through protein molecules that tell neural cells that your body temperature is too bass, says Dr. Romanovsky. Result: you are cold and your body activates with chills and other natural mechanisms to warm you up.

Although fever is a common symptom of Covid-19, some people infected with the coronavirus report chills without a fever. So if you have chills along with other common symptoms of Covid-19, such as a sore throat, runny nose, nausea and vomiting, fatigue, cough or diarrhea, this is worth worth taking a Covid-19 test, says Dr. Quinlan.

Bacterial infections

If left untreated for too long, a bacterial infection can make you really sick. This often results in a fever, but chills without a fever have also been reported in people with various infections. Usually, chills won’t be your only symptom of a bacterial infection, says Dr. Quinlan.

A life-threatening example is meningitis, which can cause chills with or without fever along with symptoms like stiff neck, sensitivity to light and sound, and lethargy. These symptoms warrant a visit to the emergency department, says Dr. Quinlan.

Another example is malaria, which can make people feel cold and chilly one minute and hot and sweaty the next. Consult a doctor if you have recently traveled to a destination where malaria is common – the CDC website maintains a list.

Sometimes people with Lyme disease also report chills without a fever, Dr. Quinlan says. If you have a history of tick bites, especially if you saw a target-shaped rash at the site of the bite, contact your doctor.

With bacterial infections, prompt treatment with the right antibiotic is essential. If you suspect this is the cause of your chills, seek medical attention immediately.

Anxiety or fear

That adrenaline rush that happens when you’re scared or super stressed? It can actually make you shiver, says Dr. Romanovsky. This is because the adrenergic nerves are part of a loop of chemical and electrical signals that temporarily activate your body’s chill response when you feel anxious or fearful. In similar ways, strong positive feelings can also give you chills.

Hypoglycemia

Low blood sugar, or hypoglycemia, can make you feel cold and shaky. “If your body doesn’t have enough sugar, it’s going to look for ways to try to get more energy and turn things on,” says Dr. Quinlan. One of those things it activates is the sympathetic nervous system, leading to symptoms like chills, sweating, heart palpitations, and blurred vision. Your GP can check your blood sugar and help you determine what is going on.

Hypothyroidism

“Your thyroid hormone is what’s really responsible for regulating your metabolism in your body, and ultimately your metabolism helps control whether you feel cold or hot,” says Dr. Quinlan. In hypothyroidism, your thyroid gland is underactive and your metabolism slows down, sometimes leaving you with chills. Other common symptoms include fatigue, weight gain, constipation, dry skin and hair, and a slow heartbeat, says Dr. Quinlan. Your GP may order a blood test to check your thyroid hormone levels.

Anemia

If you’re anemic, you’re not producing enough red blood cells, and as a result, your body isn’t moving as much oxygen as you need, Dr. Quinlan says. You may also lack iron and other important electrolytes. As a result, your sympathetic nervous system might fire up with chills to warm you up and energize you. Your primary care provider can check for anemia and prescribe treatment or iron supplements to reverse it.

Leukemia

Leukemia, a cancer of the blood-forming cells, can make some people feel cold, especially at night. The guilty? Overproduction of certain types of white blood cells that produce hormones and other factors that mimic or activate your body’s sympathetic nervous system to give you the chills.

Other common symptoms of leukemia include fatigue, frequent infections, shortness of breath, pale skin, unexplained weight loss, pain or tenderness in bones or joints, pain under the ribs on the left side, swollen lymph nodes, easy bruising and bleeding, according to the Cleveland Clinic. Blood tests, imaging tests, and biopsies can help your doctor determine if this is the cause of your symptoms.

Reactions to medications and other medical treatments

“Chills can often be related to drug reactions and can sometimes be a sign of quite severe allergies,” says Dr. Quinlan. “And so, if you’ve recently started a new medication and you’re starting to develop recurring chills, that’s a reason to talk to your doctor right away.”

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Some people experience chills after blood transfusions, some cancer treatments and some X-ray procedures as well, he says. Drug withdrawal can also cause chills in people who use narcotics or antidepressants chronically and then suddenly stop.

But there’s still one thing to consider with chills – a fever could still be on the horizon.

“At the start of a fever, we are usually cold because our body, so to speak, wants to raise the body temperature,” says Dr. Romanovsky, adding that this can take several minutes, depending on a few factors, including size. of your body. . “Shivering is like turning on the heat, but it takes time for water in a pan to get really hot.”

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