11 Reasons You Have the Chills

The most likely explanation for why you have chills is that you're cold. When your body temp goes down, your muscles contract and relax as a way to produce heat. You may also experience little tremors and goosebumps.

But the same physiological reactions can also be a sign that something is wrong. Usually it's nothing major, but, every once in a while, it can be. Here are a few of the things that can cause chills.

Emotions

You've probably had the experience many times: A piece of beautiful music or a touching story sends a chill down your spine. "The brain and sympathetic nervous system have a lot to do with getting chills," said Don Middleton, MD, vice president for family practice education at the University of Pittsburgh Medical Center, who said he had personally experienced chills from hearing bagpipes (and even thinking about it). In these cases, the chills are just a sign of a "peak" subjective emotional response, and often a good one, so there's no need to worry.

Fear or anxiety can also cause chills. This response is driven by the autonomic nervous system—the "part of your nervous system that controls involuntary actions, such as the beating of your heart and the widening or narrowing of your blood vessels," according to the National Library of Medicine's MedlinePlus resource.

A panic attack is overwhelming fear, and chills are one symptom, along with symptoms such as a pounding or racing heart, sweating, chest pain, or difficulty breathing, according to the National Institute of Mental Health. These bouts of panic can feel like a heart attack and can happen anytime, even without a clear trigger. Psychotherapy and certain medications can treat recurring panic attacks.

Infections

Having the chills is often an early red flag that you're about to get sick from a virus or bacteria, Dr. Middleton said. "Typically, it's muscle-shaking triggered by chemicals loosened either from organisms invading the body or from your own protective cells that fight off infection," he said.

Chills and repeated shaking with chills can be symptoms of COVID-19, according to the Centers for Disease Control and Prevention (CDC).

Often the chills come before a fever, giving you the odd sensation of feeling cold even though your body is burning up. Typically, chills come on at the start of an illness, so you can even have chills without fever. "When you get a virus, chills typically come at the beginning, and then you have the fever and feel generally achy," Dr. Middleton said.

Chills can also appear later, particularly if your viral load—the amount of virus in your blood sample—surges. If you find that you become significantly more ill—which includes worsening chills—after several days of feeling achy and having other symptoms of a cold, see your healthcare provider.

Fever

Chills are also often associated with a fever from different causes and can predict rising temperatures. This is most common in younger children, who develop fevers more easily, even with minor infections, according to MedlinePlus.

If you don't feel feverish or hot, chills are a helpful way to detect a rising fever. In that case, additional symptoms would include a flushed face and glassy eyes, according to the CDC.

Medication Reactions

Some people experience chills and "flu-like syndrome" after taking certain medications. "Chills may be a sign of any serious allergy to drugs, regardless of drug class," Dr. Middleton said. "Antibiotics are frequently at fault. Maddeningly, they are given to individuals who have infections, so sometimes differentiating the chills due to infection from the chills due to a drug reaction is difficult."

These reactions have also been noted with blood or blood-product transfusions, chemotherapy, and even contrast agents used for imaging tests. And they can happen when you stop medication too. "Chills may also accompany drug withdrawal, particularly from agents like narcotics or some antidepressants," Dr. Middleton said.

Low Blood Sugar (Hypoglycemia)

When your blood glucose level drops below a healthy level, you experience hypoglycemia (also known as low blood sugar or low blood glucose), according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). It's common in people with type 1 diabetes or people with type 2 diabetes who take insulin. Taking too much insulin can cause low blood sugar.

If you have mild-to-moderate hypoglycemia, you could experience a shaking chill, along with symptoms such as hunger, tiredness, dizziness, confusion, and fast or unsteady heartbeat, according to the NIDDK. But the condition can be easily treated before it becomes severe.

Intense Exercise

Physical activity can affect your body temperature and even cause a fever, according to MedlinePlus, which in turn can result in chills.

Conditions That Increase White Blood Cell Activity

White blood cells are part of your immune system, and they help fight infection and disease, according to the National Cancer Institute. Any disease that involves an increase in white blood cell activity may involve chills. This includes rheumatoid arthritis, lupus, and gout—all conditions that come with additional notable symptoms.

The increased white blood cell activity associated with these diseases leads to the release of "chemicals that cause chills, probably through triggering the hypothalamus in the brain," Dr. Middleton explained. The hypothalamus is a brain area that produces hormones that control essential processes such as body temperature, heart rate, mood, and sleep, according to MedlinePlus.

Lyme Disease

This cause is rare, but it may happen. Lyme disease is transmitted by certain types of ticks and typically occurs when an infected tick has been attached to the body for at least 36 hours. Early removal of the tick can prevent disease.

The classic early symptom of Lyme disease is the bulls-eye rash, often where the tick bit you. Other symptoms can feel a lot like the flu: chills, fever, headache, feeling sore and tired, and even vomiting. If you notice these symptoms along with the telltale rash, see a healthcare provider quickly. It's best to treat Lyme disease early.

Malaria

Chills are a classic symptom of malaria, a parasitic infection transmitted by mosquitoes. This condition is rare in the US, with only about 2,000 cases per year, according to the CDC. The transmission occurs mainly in sub-Saharan Africa and South Asia—something to be mindful of when you travel.

A typical malaria attack can include not just chills but also a fever, sweats, headache, body aches, nausea, and vomiting. These attacks recur at different time intervals; some people can go weeks or months without an attack before experiencing the chills again seemingly out of the blue.

In tropical climates, where malaria is common, patients often recognize the symptom quickly. In the US and other places where malaria is less common, it can be mistaken for the flu.

Infectious Arthritis

Also a rare condition, infectious arthritis, or septic arthritis, is joint pain that is caused by infection with bacteria, viruses, or fungi (but most commonly bacteria), and the chills can be one symptom, according to MedlinePlus.

Staphylococcus aureus bacteria (staph) commonly cause infectious arthritis. Streptococcus and even gonococcus bacteria (the same organisms that cause gonorrhea) can also cause infectious arthritis.

Cancer

Chills that you can get from cancer feel different than those you might get from other causes, such as a passing infection like a cold. "Typically for an infection, you have one or two major chills, then a fever, and you feel really bad," Dr. Middleton said. "If you have cancer, you might get a chill every night. That really means you need to see a physician."

If you do get the sort of chills Dr. Middleton described, note that the main types of cancer that could cause them are leukemia (cancer of the blood cells, according to the American Cancer Society) and lymphoma (cancer of cells that are part of your immune system, according to the American Cancer Society).