Sometimes the shivers feel great, like when caused by a passionate new romance as Ed Sheeran describes in his hit song entitled Shivers, of course. But if you start feeling cold and shaky out of the blue, you might wonder whether something is wrong. Sometimes the chills come with a fever, giving you a major clue that you’re sick. If not? You might feel even more confused.
“It’s really common, and there are a number of reasons why it happens,” says Jeffrey Quinlan, M.D., FAAFP.
Our bodies are equipped with intricate systems that tightly regulate our body temperature, keeping it in a healthy zone, which is about 36 to 37 degrees. Many problems, ranging from minor to severe, can leave you 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 doctor, because it could be a number of things,” says Dr. Quinlan.
Here are a few health concerns or circumstances that can cause chills without a fever.
Being too cold, especially from a chilly workout
OK, maybe this one’s obvious, but the most common reason for chills with no fever is that you’re actually cold. Maybe you didn’t realise your air conditioning kicked on so high, or you pushed too hard during a workout in a cold, wet climate.
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., FAPS, an Arizona State University professor and researcher who studies body temperature regulation and CEO and founder of Zharko Pharma. 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 discoordinated, 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, says Dr. Romanovsky. That’s how a toothpaste or muscle rub with menthol can give you goosebumps.)
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.
A workout in cold temperatures can also induce chills fast. 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 a fever. Infectious viruses (and bacteria, but more on those in a moment) 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.
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 Covid-19 symptoms, such as a sore throat, runny nose, nausea and vomiting, fatigue, cough, or diarrhea, it’s worth taking a Covid-19 test, says Dr. Quinlan.
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, says Dr. Quinlan.
Another example is malaria, which 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.
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.
Anxiety or fear
That surge of adrenaline that happens when you’re scared or super stressed? It can actually make you shiver, says Dr. Romanovsky. 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. Through similar pathways, strong positive feelings can also give you chills.
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.
Hypothyroidism
“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.
Anemia
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
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.
Reactions to medication and other medical treatments
“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.”
Some people experience chills after blood transfusions, certain cancer treatments, 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.
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, so to speak, 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.”
