Chills (shivering) are caused by rapid alternation between muscle contractions and relaxation. These muscle contractions are a way your body tries to warm itself up when you’re cold.

Chills are often, though not always, associated with fever. Sometimes, they precede the onset of fever, especially if the fever is caused by an infection. Other times, they occur without a spike in temperature. Chills may or may not be serious, depending on the underlying cause.

Chills without fever can be caused by a number of conditions.

1. Exposure to cold

You may experience chills because you are in a very cold place, such as the ocean or a pool, or outside on a chilly day. You can also get chills if your clothing becomes damp or wet. You can get chills indoors, too, if the air-conditioning is set too cold or the heat isn’t hot enough.

As the human body ages, it has a more difficult time regulating body temperature, even in healthy older adults. Medical conditions such as diabetes and heart disease can make the problem worse.

These types of chills should dissipate as soon as your body warms up. However, if you experience continual shaking when you have been exposed to intense cold, you may have developed complications such as hypothermia or frostbite, which are both potentially serious.

Other symptoms of these conditions can include:

  • numbness
  • changes in skin color
  • slurred speech
  • extreme drowsiness
  • stinging or burning sensation, particularly in the fingers, toes, ears, or nose
  • blisters

Seek immediate medical help if you suspect hypothermia or frostbite.

2. Medication side effect

Chills without fever may result from taking certain medications or combinations of medications. They may also occur if you take the incorrect dosage of an over-the-counter medication, herbal supplement, or prescription drug.

Always read the potential side effects information included with medication packaging. If you suspect that you’re having chills because of a drug or drugs you use, let your doctor or pharmacist know immediately. Depending on the severity, you may require medical attention.

3. Reaction to extreme physical activity

Marathon running or other forms of extreme sports that require intense physical exertion may cause changes to your core body temperature. That can result in chills.

This response can happen in any type of weather but may be more likely to occur in very cold or very hot temperatures:

In both instances, other symptoms you might experience include:

  • goosebumps
  • muscle cramping
  • dizziness
  • fatigue
  • nausea and vomiting

You can avoid chills from exercise by remaining hydrated and dressing appropriately for your workouts. Consider avoiding exercise during the coldest or hottest times of day and also limiting the duration of time spent in intense activity.

Hydrating and getting your temperature back into a normal range are usually enough to eliminate your symptoms.

In some instances, though, you may require IV fluids to treat the condition.

4. Hypothyroidism (underactive thyroid)

An underactive thyroid is a thyroid gland that doesn’t produce enough of the hormones needed to regulate metabolic rate or support overall health. This condition can cause an increased sensitivity to cold, resulting in chills.

Additional symptoms associated with hypothyroidism include:

  • puffiness in the face
  • unexplained weight gain
  • dry skin, nails, and hair
  • muscle weakness, pain, or stiffness
  • depression or feelings of sadness
  • trouble with memory
  • constipation

Hypothyroidism is diagnosed through a blood test. It’s a treatable condition and typically requires daily medication.

5. Hypoglycemia

Hypoglycemia occurs if blood sugar levels dip abnormally low. If you have diabetes, it may be a sign that your medication or diet needs to be adjusted. It’s also possible to experience hypoglycemia without diabetes.

Hypoglycemia requires immediate treatment to get blood sugar levels back to normal. One of the symptoms of hypoglycemia is a feeling of shakiness or muscle weakness, which may mimic chills. Other symptoms of this condition include:

  • sweating
  • irritability
  • heart palpitations
  • tingling feelings around the mouth
  • confusion
  • seizures
  • blurred vision

6. Malnutrition

Malnutrition occurs when your body lacks necessary nutrients. This can happen because of poor access to nutritious foods, an underlying condition that affects your body’s ability to properly absorb nutrients, or an eating disorder, like anorexia. Without the correct balance of nutrients, your body can’t properly function.

Other symptoms of malnutrition include:

  • fatigue or sleepiness
  • weakness
  • difficulty concentrating
  • pale skin
  • rashes
  • heart palpitations
  • feeling faint or lightheaded, or fainting
  • tingling or numbness of the joints or extremities
  • in women, missed periods, heavy menstrual cycles, or infertility

Talk to your doctor if you suspect malnutrition. This is a serious condition that can lead to complications if left untreated.

7. Emotional reaction

Chills can occur if you have a profound or intense emotional reaction to a situation. Emotions that might cause chills include fear or anxiety.

Chills can also be caused by experiences that move you deeply in a positive way, such as listening to music or inspirational words.

This is sometimes referred to as a “frisson.” It may also be called “chills going up the spine” or “goosebumps.” This type of emotional reaction may be caused by neurobiological mechanisms that trigger the release of dopamine, a neurotransmitter.

Chills without fever can become serious if you’re experiencing frostbite or hypothermia. These conditions can quickly become a medical emergency requiring immediate intervention or care.

Other conditions that cause chills, such as hypothyroidism, require medical support but may not warrant a visit to the emergency room. If you have the symptoms of this thyroid condition, make an appointment to see your doctor and ask about getting a diagnostic blood test.

If you have symptoms of hypoglycemia but haven’t been diagnosed with diabetes, contact your doctor or call your local emergency medical services immediately. If you have diabetes and hypoglycemia symptoms that don’t improve with at-home treatment, seek medical help immediately.

If you have diabetes and your chills are caused by hypoglycemia, take a glucose tablet if you have one. Other ways of balancing your sugar levels include drinking orange juice or regular soda, or eating a few pieces of candy.

If your chills are caused by extreme cold, make sure to get yourself dry if you are wet. Layer up and make sure to cover your head, hands, and feet so that you can capture and maintain as much body heat as possible. Soaking in a warm bath may also help alleviate chills caused by extreme cold. Just make sure to put on warm, dry clothes after you’re done bathing.

If your chills don’t dissipate quickly, talk to your doctor about other treatments that might help.

Chills without fever can often be rectified with at-home treatments or with modifications of behaviors, such as changing your workout routine. They may also be a sign of a medical condition that requires treatment.

Talk to your doctor if you have chills that don’t go away or if you regularly experience unexplained chills.