Chills and shaking are common physical sensations. Chills describe a feeling of coldness, sometimes with goosebumps, even when the environment is not cold. Shivering involves involuntary muscle contractions that generate heat. These responses are typically signs of the body reacting to various internal or external stimuli.
The Body’s Temperature Defense
The human body maintains a stable internal temperature through thermoregulation, primarily controlled by the hypothalamus, the brain’s thermostat. When the body senses it is too cold, it initiates heat-generating mechanisms. Shivering, a prominent mechanism, involves rapid, involuntary skeletal muscle contractions. This muscle activity produces heat, effectively warming the body.
This heat-generating response occurs in two main scenarios. When exposed to a cold environment, such as hypothermia, the body shivers to counteract heat loss and raise its core temperature. During a fever, the hypothalamus raises the body’s temperature set point in response to certain substances. As the body’s current temperature is below this new target, a person feels cold and shivers to reach the elevated temperature.
Infections and Illnesses
Infections are a common reason for chills and shaking. When the immune system detects pathogens, like bacteria or viruses, it releases pyrogens. These pyrogens signal the hypothalamus to increase the body’s temperature set point, leading to a fever. Fever is the body’s natural defense, creating an environment less favorable for microbial growth.
Many common infections can trigger this response, including the flu, common cold, pneumonia, and urinary tract infections (UTIs). More serious bacterial or viral infections, such as sepsis or meningitis, can also induce fever with accompanying chills and shaking.
Non-Temperature Related Causes
Chills and shaking can also stem from causes not directly related to temperature regulation. Low blood sugar, or hypoglycemia, is one such cause. When blood glucose levels drop too low, the body releases stress hormones like adrenaline, leading to shakiness, sweating, and anxiety. This signals a need for glucose.
Anxiety, stress, and panic attacks can also manifest with physical symptoms like trembling, shaking, and chills. This occurs due to the “fight or flight” response, which releases adrenaline and other hormones, preparing the body for perceived danger.
Certain medications can also cause tremors or chills as side effects. These drug-induced tremors result from the medication’s effects on the nervous system or neurotransmitters.
Withdrawal from alcohol or certain drugs can also cause significant shaking and chills as the body adjusts. This is often due to a neurotransmitter imbalance in the brain. Thyroid conditions, such as hyperthyroidism, can cause tremors due to increased metabolic activity and nervous system stimulation. Some neurological conditions may also present with shaking or involuntary movements.
When to Seek Medical Attention
While chills and shaking are often benign, certain accompanying symptoms or persistent patterns warrant medical evaluation. Seek medical attention if a fever is high (over 103°F/39.4°C in adults) or persists for more than three days. For infants under three months, any temperature of 100.3°F (38°C) or higher requires immediate medical contact.
Other concerning signs include:
Severe pain accompanying chills
Difficulty breathing or chest pain
Confusion or altered mental state
A stiff neck
A severe headache
Chills without an obvious cause, or if they are severe or repeated
Worsening symptoms or inability to keep down fluids