Fever is the body turning its own thermostat up.
A small part of the brain keeps the body near 37 °C. When germs get in, the immune system sends messages that turn that setting up, and the body shivers and holds on to heat until it reaches the new mark. Fever is a sign that something is being fought, not an illness in itself.
In plain words.
A reading of 38 °C (100.4 °F) or more is a fever. How high it goes does not tell you how serious the cause is. How you are otherwise, and how long it lasts, matter more.
Most fevers in adults are caused by viruses and settle within three to five days with rest, plenty of fluids and paracetamol. Antibiotics do not work on viruses.
In India some fevers need a blood test early, because the cause changes what must be done: dengue, malaria and typhoid, above all in and after the monsoon, and urine or chest infections. A fever that lasts more than three days, or comes with any warning sign below, should be tested rather than waited out.
The body’s thermostat
The thermostat in the brain is set near 37 °C. The body makes heat and loses it in balance, so the reading hardly moves through the day.
Germs set off messengers from the immune system that turn the setting up. The body shivers and holds heat in until it reaches the new mark. Paracetamol turns the setting down for a few hours; it does not treat the cause.
Go to hospital now if
- A stiff neck, a new severe headache, confusion or unusual drowsiness, or a fit: call 112.
- A purple or dark red rash that does not fade when a glass is pressed on it: call 112.
- Breathlessness, chest pain, or lips turning blue: call 112.
- In a dengue-like fever: severe tummy pain, vomiting again and again, bleeding from the gums or nose, vomiting blood or black stools, restlessness or drowsiness, or cold, clammy hands and feet. These are warning signs, often around the time the fever comes down: go to hospital now.
- You cannot keep fluids down, pass very little urine, or feel faint on standing.
- Fever while on chemotherapy, or on medicines that lower immunity: go to hospital now.
Call 112 or go to the nearest emergency department. Ambulance: 108 (102 in some states).
See a doctor within a day if
- The fever has lasted more than three days
- It comes with burning urine, or pain in the side or back
- You are pregnant, over 65, or have diabetes, kidney, liver or heart disease
- It started after travel, or keeps coming back
- It comes with yellow eyes or dark urine: see a doctor the same day
Tests that help.
Not everyone needs every test. He decides which ones are worth doing for you.
| Test | What it tells |
|---|---|
| Complete blood count (CBC) | White cells and platelets. Low platelets point towards dengue; a high white count towards a bacterial infection. |
| Dengue NS1 and IgM | NS1 works best in the first five days; the IgM antibody test after about day five. |
| Malaria test | A rapid card test or a blood smear, done as soon as malaria is suspected. Do not wait for a shivering bout. |
| Typhoid | A blood culture in the first week is the reliable test. The Widal test is often misleading: one positive Widal is not proof of typhoid. |
| Urine routine and culture | For a urine infection, a common hidden cause of fever. |
| Liver and kidney tests, chest X-ray | When the fever is severe, lasting, or comes with cough or breathlessness. |
Have it ready.
Tick them off as you gather them. The ticks stay on this phone only.
Online, or in person?
For fever, paracetamol is the safer choice; keep to the dose on the pack, as too much harms the liver. Avoid ibuprofen, diclofenac, nimesulide or aspirin until dengue has been ruled out: they raise the risk of bleeding.
A video call can
- Work out the likely causes from the pattern and your other symptoms
- Decide which tests are needed, and on which day of the fever
- Read the reports with you, and follow platelets day by day in dengue
- Tell you plainly when home care is enough and when to go in
Needs a visit in person
- Examining the chest, tummy and throat when the cause is unclear
- Blood tests, at a laboratory or by home collection
- A drip (IV fluids) for dehydration, or dengue with warning signs
- Any warning sign in the red box: that is an emergency
Talk it through with Dr. Arya.
Bring your reports and medicines to a video consultation. He goes through them with you, in plain words, and says clearly if you need to be seen in person.
Book a video consultationDr. Prabhat Arya · MBBS, MD (Internal Medicine) · Delhi Medical Council Reg. No. DMC-83759