Body aches and chills usually mean your immune system is actively fighting something, most often a viral infection like the flu or COVID-19. The combination feels miserable, but it’s actually your body’s defense mechanism working as designed. In some cases, though, these symptoms can point to something other than a common virus, including bacterial infections, low blood sugar, or environmental exposure to cold.
Why Your Body Reacts This Way
When your immune system detects a threat, it releases signaling molecules called cytokines. These cytokines act on your brain’s temperature control center, the hypothalamus, and essentially trick it into raising your body’s thermostat. The hypothalamus responds by activating your skeletal muscles to contract rapidly, which is the shivering you feel. That shivering generates heat to bring your core temperature up to its new, higher set point.
The chills you experience are the sensation of your current body temperature being “too low” relative to where your brain now thinks it should be. That’s why you can feel freezing cold even when your skin is warm to the touch. Meanwhile, the same cytokines that trigger fever also cause inflammation in your muscles, which is why your whole body can ache during an infection. The soreness isn’t from the virus itself damaging your muscles. It’s collateral damage from your own immune response.
Infections: The Most Common Cause
Respiratory viruses top the list. The flu typically causes symptoms one to four days after exposure and is frequently accompanied by intense body aches and higher fever than most other common viruses. COVID-19 follows a similar pattern but with a slightly longer incubation period of two to five days, sometimes up to 14. Both can cause fever, chills, muscle pain, fatigue, and cough. The common cold can also cause mild aches and chills, though they tend to be less severe.
Bacterial infections are another possibility, especially if your symptoms are lingering or worsening. A few patterns suggest bacteria rather than a virus: symptoms lasting longer than the 10 to 14 days a virus typically takes to resolve, a fever that climbs higher than you’d expect, or a fever that gets worse several days into the illness rather than gradually improving. Urinary tract infections, strep throat, and pneumonia are bacterial infections that commonly cause chills and body aches.
Lyme disease is worth knowing about if you live in or have visited a tick-prone area. Early Lyme disease causes fever, chills, headache, fatigue, and muscle and joint aches. While most people associate it with a bull’s-eye rash, that rash only appears in about 70 to 80 percent of cases, meaning roughly one in four people with Lyme never develop the telltale skin sign.
Causes That Aren’t Infections
Not every case of body aches and chills means you’re sick with an infection. Several other conditions can produce similar symptoms.
- Cold exposure. When your body temperature drops, shivering kicks in automatically as a defense against hypothermia. If you’ve been outside in cold weather and you’re shivering with stiff, achy muscles, warming up gradually is the priority. Shivering is the first sign that hypothermia is starting.
- Low blood sugar. Hypoglycemia, defined as blood glucose below 70 mg/dL, can cause shakiness that feels a lot like chills. It often comes with sweating, confusion, a racing heartbeat, blurry vision, and lightheadedness. This is most relevant if you have diabetes or haven’t eaten in a long time.
- Intense anxiety or panic attacks. Strong emotional reactions, particularly fear and anxiety, can trigger chills along with shortness of breath, heart palpitations, sweating, and chest pain. If the chills come on during moments of high stress and resolve when you calm down, anxiety may be the driver.
- Autoimmune flare-ups. Conditions like lupus and rheumatoid arthritis can cause body-wide aches and sometimes chills during active flare periods, since the underlying mechanism involves the same inflammatory cytokines that infections trigger.
How Long Body Aches Typically Last
For most viral infections, the worst of the body aches and chills resolves within three to seven days. Flu body aches tend to peak in the first two to three days and then gradually ease, though fatigue can linger for a week or two after. COVID-19 follows a similar arc for most people, though some experience prolonged fatigue and muscle soreness. If your aches are still intensifying after a week, or you’re developing new symptoms rather than improving, that’s a sign your body may be dealing with something beyond a standard virus.
What You Can Do Right Now
Over-the-counter pain relievers like acetaminophen and ibuprofen are effective at reducing both the aches and the fever driving your chills. If you’re taking acetaminophen, stay under 4,000 milligrams total in 24 hours, and check the labels of any other medications you’re using since many cold and flu products also contain acetaminophen. Doubling up without realizing it is one of the most common causes of accidental overdose.
Beyond medication, the basics matter: stay hydrated, rest, and layer blankets if the chills are making you uncomfortable. Fever is your body’s way of creating a hostile environment for pathogens, so a moderate fever doesn’t necessarily need to be brought down unless it’s making you miserable. Eating small, easy meals helps keep your blood sugar stable, which prevents the shakiness that can layer on top of infection-related chills.
Signs That Need Urgent Attention
Most cases of body aches and chills resolve on their own, but certain combinations of symptoms signal something more dangerous. Sepsis, a life-threatening response to infection, can start with shivering and body aches but progresses to fast and shallow breathing, confusion, extreme sleepiness, sweating for no clear reason, and lightheadedness. These symptoms need emergency care.
Call your doctor if your fever exceeds 104°F (40°C). Seek immediate medical help if your chills and aches are accompanied by confusion, a stiff neck, seizures, loss of consciousness, trouble breathing, severe pain, or painful urination with foul-smelling urine. A fever that keeps climbing after several days of illness, rather than tapering off, also warrants a call since it may indicate a secondary bacterial infection that needs treatment.