High temperature (fever) in adults
A high temperature is not an illness but the way the body answers an infection or inflammation: in those conditions the immune cells work better and many…
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Medicines commonly prescribed for High temperature (fever) in adults
For informational purposes only. Always consult a doctor before taking any medication.
Dosage form: EFFERVESCENT TABLET, 1000 mgActive substance: paracetamolManufacturer: Industria Quimica Y Farmaceutica Vir S.A.Prescription requiredDosage form: ORAL SOLUTION/SUSPENSION, 40 mg/mlActive substance: ibuprofenManufacturer: Reckitt Benckiser Healthcare S.A.Prescription not requiredDosage form: ORAL SOLUTION/SUSPENSION, 100 mg/mlActive substance: paracetamolManufacturer: Kern Pharma S.L.Prescription not required
A high temperature is not an illness but the way the body answers an infection or inflammation: in those conditions the immune cells work better and many microbes work worse. So the question that matters here is not what the thermometer says but what is happening to the person alongside that temperature. An adult can walk about and work at 39C and can be seriously ill at 37.8C, and it is the second case that is worrying. This page is about adults; a high temperature in a child is covered on a separate page, "High temperature (fever) in children", because both the warning signs and what to do about them are different there.
Call an ambulance immediately if
A high reading on its own does not call for an ambulance. A temperature together with any of the following does mean help is needed now:
- a rash of small red or purple spots and blotches has appeared that does not fade when you press the bottom of a clear glass against it;
- severe headache with a stiff neck, when the chin cannot be brought down to the chest, and light hurting the eyes;
- confusion, delirium, unusual behaviour, slurred speech, or the person is hard to wake;
- breathing is hard work, fast and shallow, and a whole sentence cannot be finished in one breath;
- the skin has turned mottled, grey or bluish, the lips have gone blue, and the hands and feet are icy while the body is burning;
- no urine has been passed for twelve hours;
- a seizure that has never happened before;
- chest pain, or such a sudden collapse of strength that the person cannot stand or hold their head up.
112 is the single European emergency number and works in Spain, Italy, Portugal, Poland and Ukraine; elsewhere dial your local emergency number. Tell the call handler what the temperature is, how long it has been there and what exactly has frightened you.
Sepsis, which is what that list is for
Sepsis is not "blood poisoning by germs", as people tend to picture it, but the body's own destructive answer to an infection: the immune reaction runs out of control and starts damaging its owner's blood vessels and organs. It can start from anywhere — pneumonia, a urine infection, a wound that has turned septic, a bad tooth — and it moves fast, over hours.
What gives it away is that the person looks and feels disproportionately ill for an ordinary cold. The worrying features are confusion and drowsiness, shivering with a feeling of bitter cold, very fast breathing, a racing pulse, a sharp drop in the amount of urine passed, mottled or ashen skin, and the person's own sense that they are dying. One important detail: the temperature in sepsis is not always high. In older and frail people it can be normal or even low, and that is more alarming still.
The risk is greater with diabetes, cirrhosis, kidney failure, after chemotherapy, in anyone taking steroids or other medicines that damp down immunity, in people whose spleen has been removed, in pregnancy and just after childbirth, and in the elderly. If you suspect sepsis, say the word out loud when you call the ambulance or arrive at hospital: it triggers a pathway of its own, and here the clock runs in hours.
Three situations where a temperature is not sat out
There are circumstances in which even a moderate temperature with no other complaint means being seen the same day, and sometimes straight away.
- Coming back from the tropics. Any fever after travelling to a country where malaria occurs means being tested immediately rather than reaching for a paracetamol. Malaria starts like ordinary flu — temperature, chills, aching, headache, sometimes diarrhoea — and untreated, the severe form can kill within a day. The attack may come weeks or even months after you get home, so always tell the doctor where you have been in the past year, even if the trip feels like ancient history. Preventive tablets do not rule the illness out. Other fevers matter after the tropics too, from dengue to typhoid, and they need sorting out somewhere that can run a blood test the same day.
- Recent surgery, a catheter or an implant. A temperature in the first weeks after an operation, or in anyone with a urinary or intravenous line, a joint replacement or a heart valve, is always a reason to be seen rather than to blame a cold. Look at the surgical wound while you are at it: redness, swelling, pain and discharge speak for themselves.
- Chemotherapy and treatment that suppresses immunity. The rule here is the strictest of all. If you are having chemotherapy, taking immunosuppressants or on high-dose steroids, a temperature is an emergency and not a household nuisance. This is neutropenic fever: the white cells that hold infection in check are all but gone, and an everyday bacterium can produce sepsis within hours. No waiting until morning, and nothing to bring the temperature down and blur the picture: contact your treatment team or go straight to hospital. The same goes for anyone without a spleen.
What the thermometer shows and what it does not
Normal body temperature differs from person to person and changes through the day: lower in the morning, close to a degree higher by the evening. A temperature of 38C or above is taken as high, but that is an agreed line rather than a boundary where danger begins. Your own sensations are a fair guide too: if you are shivery, flushed, aching and hot to the touch, you probably do have a temperature even when the thermometer says otherwise.
Use a digital thermometer under the tongue or in the armpit with the arm held firmly against the body; ear thermometers are convenient but need the instructions followed exactly. Forehead strips are not worth relying on, as they are not accurate. After a hot bath, exercise or a cigarette, wait twenty minutes or the reading will be falsely high.
And the main point: the number itself says very little about how ill someone is. Severe pneumonia can run at 37.5C and a harmless viral infection at 39.5C. What is watched is not the column of the thermometer but breathing, alertness, skin colour, urine, and how quickly things are changing. A temperature is brought down to make you feel better, not to produce a tidy figure.
Why a temperature goes up
Most often from infection, and in the great majority of cases a viral one: a cold, flu, a stomach bug. That kind of temperature lasts two or three days and goes away by itself. Bacterial infections — pneumonia, tonsillitis, a kidney infection, cellulitis, an infected wound — usually give a more persistent fever and an obvious place to point at: something hurts, something is discharging, something is red.
But fever also happens without infection:
- inflammatory and autoimmune diseases, from rheumatoid arthritis to the vasculitides;
- deep vein thrombosis in the calf and pulmonary embolism: here the temperature comes with a swollen, painful calf or with sudden breathlessness;
- drug fever, a reaction to a medicine, often an antibiotic started a week or two earlier;
- an overactive thyroid, tumours and blood disorders, in a long fever with no obvious source;
- extensive burns, injuries and recent vaccinations, where the temperature lasts a day and settles.
Overheating is a separate matter. Heatstroke is not fever: the body has not turned the temperature up, it has failed to cope with the heat. It happens in hot weather, in stuffy rooms, and while working or exercising in the sun, and it shows as confusion, headache, nausea, hot skin and sweating that has stopped. Here, unlike in fever, the person genuinely is cooled — moved into the shade, undressed, fanned, with something cold at the neck and armpits — while an ambulance is called.
What to do at home
If none of the warning signs are there, a temperature is ridden out at home, and the aim is simple: feel better and do not get dehydrated.
- Drink more than usual and in small amounts: with a temperature and sweating, fluid goes quickly. The guide is easy — your urine should stay pale.
- Rest. Carrying a fever around and working through it is a reliable way to make the illness last longer.
- Dress lightly and air the room. Wrapping up during the shivery phase is understandable, but do not end up overheated.
- If you feel rotten, achy and headachy, paracetamol or ibuprofen will help. Take them as the packet says, to feel better rather than to lower the number, because the temperature itself is doing no harm.
- Eat as much as you fancy and no more.
- While the temperature lasts, stay at home and keep away from other people: you are infectious.
What not to do. Do not sponge yourself with cold water, alcohol or vinegar and do not get into a cold bath: the skin's blood vessels clamp shut, shivering starts, and body temperature goes up rather than down, while alcohol is also absorbed through the skin. Do not alternate paracetamol and ibuprofen by the clock as a matter of routine, as it doubles the chance of a dosing mistake and gains nothing; that is done only when a doctor says so. Ibuprofen and the other anti-inflammatories are best avoided if you are dehydrated or have kidney disease, a stomach ulcer or chickenpox. And do not carry any of this across to a child: adult preparations are not suitable for them, aspirin is not given to children or adolescents at all, and their warning signs are different ones, set out on the neighbouring page, "High temperature (fever) in children".
When you need a doctor the same day
An ambulance is rarely needed, but it is worth being seen without delay in these cases:
- the temperature has lasted more than three days and is not settling, or it has climbed again just as you were recovering;
- by the third or fourth day you are clearly worse rather than better;
- there is a specific symptom alongside it: stinging or pain on passing urine or loin pain, a cough with phlegm and chest pain on breathing in, a severe sore throat, tummy pain, yellowing of the skin, a swollen painful calf, any new rash;
- the temperature appeared a week or two after starting a new medicine;
- you are pregnant, over sixty-five, or living with diabetes or heart, lung, kidney or liver disease;
- the fever keeps returning in waves over weeks, or you are losing weight and sweating at night;
- you simply feel that something is wrong. That is not being oversensitive; it is often the earliest sign there is.
Online consultation
A temperature is exactly the sort of thing where talking to a doctor at a distance saves both time and worry. In an online consultation the doctor will establish how it started and how it is changing day by day, ask about travel, operations, medicines and long-term conditions, help you tell an ordinary viral infection from one that needs examining and testing, say which investigations are worth doing and in what order, and suggest how to feel better without extra drugs. Separately they will spell out the signs that, for you specifically, mean stopping the watchful waiting and calling an ambulance, which is the most useful thing to take away from such an appointment. If there is a rash that does not fade under a glass, confusion, laboured breathing, or a temperature during chemotherapy, an online appointment is not what is needed — an ambulance is.
This material is for information only and does not replace medical advice.
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