General
Chills and shivering
A feeling of being cold with shivering or shaking, usually as the body raises its temperature to fight an infection — most often a harmless viral illness, but occasionally, when shaking is violent and accompanied by high fever and confusion, a warning sign of a dangerous infection.
Education and reference only. This explains the common causes of chills and shivering and the warning signs that need urgent help, in plain language — it is not a diagnosis or a substitute for advice from a clinician. If you feel very unwell or are worried, seek medical help.
Quick answer
What is chills and shivering?
Chills are the sensation of feeling cold and shivering, and they most often appear at the start of a fever as the body works to raise its core temperature to fight off an infection. Mild chills with a common cold or flu are usually nothing to worry about and settle as the illness passes.
- Get urgent help: Call 999 or go to A&E if violent shivering and a high fever come with confusion, slurred speech, very fast breathing or a feeling that something is seriously wrong — this can be sepsis. Seek urgent help for a fever with chills after travel to a country where malaria is found, even weeks later.
- Self-care: For chills that come with an ordinary viral illness, rest, keep warm with light layers you can adjust, and drink plenty of fluids to stay hydrated, as fever increases the body's fluid needs.
About chills and shivering
Chills are the sensation of feeling cold and shivering, and they most often appear at the start of a fever as the body works to raise its core temperature to fight off an infection. Mild chills with a common cold or flu are usually nothing to worry about and settle as the illness passes. The pattern and severity, though, can matter a great deal. Violent, uncontrollable shaking — known as a rigor — together with a high fever is the body responding to a significant infection, and when it comes with confusion, fast breathing, a fast heartbeat or a feeling of being very unwell, it can be a sign of sepsis, a life-threatening response to infection that needs emergency treatment. Chills with a fever after returning from a country where malaria is found should always prompt urgent assessment, as malaria can become serious quickly. Most chills, however, accompany ordinary self-limiting infections.
When to get help
Call 999 or go to A&E if chills and shivering comes with any of these warning signs:
- Call 999 or go to A&E if violent shivering and a high fever come with confusion, slurred speech, very fast breathing or a feeling that something is seriously wrong — this can be sepsis.
- Seek urgent help for a fever with chills after travel to a country where malaria is found, even weeks later.
- Seek urgent help for a rash that does not fade when pressed under a glass, alongside fever and chills.
- Seek urgent help for chills and fever with severe back or side pain, or pain and burning on passing urine.
- Seek urgent help if a baby, young child or frail older person has chills and a fever and seems very unwell, drowsy or is not feeding.
When to see a doctor
Treat violent shaking and high fever with confusion, fast breathing or a feeling of being gravely unwell as an emergency and call 999, as this can be sepsis. Seek urgent help for fever and chills after travel to a malaria area, for a rash that does not fade under glass, or for severe back or side pain. For chills with an ordinary cold or flu in an otherwise well adult, self-care at home is usually enough, but arrange an appointment if the fever lasts more than a few days, keeps returning, or you are getting steadily worse.
Not sure how urgent it is? It is always OK to call NHS 111 for advice, day or night.
What can cause it
Common causes of chills and shivering
Chills and shivering has many possible causes. Each links to a full, plain-language guide to that condition — what it is, how it's treated and when to seek help.
What helps
Self-care and what you can do
For chills that come with an ordinary viral illness, rest, keep warm with light layers you can adjust, and drink plenty of fluids to stay hydrated, as fever increases the body's fluid needs. Avoid piling on too many heavy blankets if you also have a high fever, as this can trap heat; aim to feel comfortable rather than overheated. Eating little and often is fine if your appetite is reduced. Keep an eye on how unwell you feel overall rather than the thermometer alone, and rest until your strength returns. If you have recently travelled abroad, make a note of where and when, as this information is important for your clinician should you need to be seen.
Answers
Chills and shivering: frequently asked questions
Why do I shiver when I have a fever?
Shivering is the body generating heat by making the muscles work, which raises your core temperature as part of fighting an infection. It often comes at the start of a fever and tends to settle as the temperature rises.
When are chills a sign of something serious?
Violent, uncontrollable shaking with a high fever, especially with confusion, fast breathing or feeling gravely unwell, can be a sign of sepsis and is an emergency. Fever and chills after travel to a malaria area also need urgent assessment.
Should I wrap up warmly or cool down when I have chills?
Keep comfortable with light, adjustable layers. While chills make you feel cold, piling on heavy blankets when you also have a high fever can trap heat. Aim to feel comfortable rather than either shivering or overheating.
Can chills happen without a high temperature?
Yes, you can feel cold and shivery as a fever is building, before the thermometer rises. How unwell you feel overall is a better guide than the temperature alone, so seek help if you feel very unwell.
Sources
Where this is drawn from
- NICE CKS: Feverish illness in adults.
- UK Sepsis Trust: spotting sepsis.
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