When people are cold, the muscles in their body will contract and relax rapidly to generate heat. This causes part or all of the body to shiver or shake. People can still shiver on a warm day if there is a cool breeze or they are sitting in the shade.
Shivering is an involuntary movement of the body, which means that it is uncontrolled. Hiccups and sneezing are other examples of involuntary movements.
Read on to learn about eight causes of shivering and when it is necessary to see a doctor.
What causes shivering?
Shivering occurs most commonly when a person is cold. It is usually temporary and should stop once the individual warms up.
However, shivering can also be a symptom of physical or mental illness.
Below are eight potential causes of shivering:
A fever may cause shivering.
Other than being cold, the most common cause of shivering is fever, which doctors define as a body temperature higher than 100°F.
Fever usually occurs as a result of infection, but inflammation or an allergic reaction can also increase body temperature. Some people with a fever may also have signs of flu, but others will have no additional symptoms.
Drinking plenty of fluids and taking nonsteroidal anti-inflammatory drugs (NSAIDs) can help to reduce a temperature.
If a person has other symptoms, particularly a stiff neck, rapid heartbeat, or shallow breathing, they should seek medical advice within 24 hours. If they have no other symptoms, they will only need to visit a doctor if the fever lasts for more than 3 days.
2. Psychogenic movement disorders
For some people, stress or mental health factors can cause shivering and other involuntary movements. This usually occurs due to a psychogenic movement disorder, which can affect any part of the body.
A doctor who specializes in medical conditions affecting the brain, called a neurologist, will usually diagnose psychogenic movement disorders. They may look for the following characteristics when making a diagnosis:
- movements happening suddenly, without warning
- memories of a traumatic event triggering movements
- movements stopping if a person is distracted
- underlying mental health issues, such as depression
There is often no underlying brain or nerve damage. Instead, shivering is the body’s response to stress.
Doctors will often treat psychogenic movement disorders with a combination of mental health therapy and physical therapy.
3. Postanesthetic shivering
A person may shiver when recovering from an anesthetic.
Shivering can occur when a person regains consciousness after a general anesthetic.
A person’s temperature may drop during a surgical procedure, which can cause them to shiver when they wake up after the operation is over.
Anesthetics can also affect the body’s ability to regulate temperature, which can make it difficult for the body to warm up quickly after an operation.
Doctors will usually check a person’s temperature and provide them with blankets or heaters if necessary.
4. Fear, excitement, or stress
Strong emotions can cause a person to shake or shiver. This is often due to a surge of adrenaline in the body. Adrenaline is a hormone that triggers the body’s fight-or-flight response.
Shivering should stop after the adrenaline leaves the body. For many people, this will happen very rarely, perhaps during a particularly exciting or frightening moment. For those who experience chronic stress, adrenaline surges and shaking can be more frequent.
Involuntary trembling, shaking, or shivering can be due to a medical condition called essential tremor. Essential tremor is a neurological condition, meaning that it relates to the brain.
This condition affects approximately 10 million people in the United States and can cause trembling in the hands, legs, body, or voice.
Tremors can also be a symptom of Parkinson’s disease. This is a disorder that affects an area of the brain and tends to develop gradually.
6. Low blood sugar
If a person has not had food or water for a long time, the level of glucose in their blood can drop. This low blood sugar can cause shivering or shaking.
For people who have diabetes, this will be known as hypoglycemia, and it can be severe. People with diabetes should check their blood glucose regularly to prevent their levels from dropping too low.
Anxiety is a mental health condition that can affect the body as well as the mind. It can cause physical symptoms, such as nausea, increased heart rate, and shivering or shaking.
Treatment for anxiety may include therapy, medication, and lifestyle changes. Activities that might help a person to manage their anxiety include exercising, listening to music, and spending time with supportive friends and family.
Sepsis may require hospital treatment.
Sepsis is an overwhelming response of the body to infection, and it often occurs in connection with lung, skin, gut, or urinary tract infections.
One of the symptoms of sepsis is shivering. Other symptoms include confusion, feeling sweaty or clammy, pain, raised heart rate, and shortness of breath.
Sepsis is a medical emergency. People with sepsis will need prompt treatment with antibiotics in a hospital.
Treating shivering at home and when to see a doctor
Shivering is usually temporary. If it occurs due to a fever, low blood sugar, or a strong emotion, it should resolve once a person treats the underlying cause. They can:
- treat a fever with fluids and NSAIDs
- eat to restore blood sugar levels
- sit down somewhere quiet and breathe slowly to calm strong emotions
Other causes of shivering may be due to an underlying medical condition. If a person is concerned, they should note any other symptoms and seek medical advice.
Shivering can be a more severe symptom for older adults or people with an underlying health condition. Older adults are often less able to regulate their body temperature so they may become cold more quickly. Keeping warm in cold weather is essential for good health.
Fever increases the heart rate and makes breathing faster. This can be serious if a person has a heart or lung condition.