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Side effects — during treatment
Feeling Cold, Shivering or Excessive Sweating During Radiation — Is It Fever, or Is It Nerves?
Chills and sweats during a course of radiation are common, and most have a simple explanation. One does not. Before anything else, take the temperature. A reading of 38°C (100.4°F) or above, or shaking chills that rattle the bed, means calling 1800 202 8726 now rather than waiting for the next session.
Medically reviewed by Dr. Venkata Sushma P, Radiation Oncologist, MBBS · MD (Radiation Oncology) · Last reviewed August 2026
- Thermometer first, theory second — the one question that decides everything is whether there is a fever. This page tells you what to measure, when, and which number changes the plan.
- Infection is the differential that matters — chills during cancer treatment can be the earliest sign of an infection in the blood, sometimes before the temperature climbs. We give you the threshold in plain numbers.
- Nerves are a real cause, not an excuse — anxiety genuinely makes you cold and clammy around a session. We show how an anxiety chill differs from an infection chill, so you can tell them apart at home.
- Written for whoever is in the room — a spouse or carer can use the same table at 11pm without medical training, and know whether this is a call, a hospital trip, or a note for the weekly review.
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Take the temperature before you read any further. During cancer treatment, a reading of 38°C (100.4°F) or above, shaking chills that rattle the bed, or feeling cold and unwell with a racing pulse can be the first sign of an infection in the bloodstream.
Call 1800 202 8726 now — or go straight to the nearest emergency department. Say the words “cancer patient on radiation treatment, with fever” at the desk, because that sentence changes how quickly you are seen.
Do not take anything to bring the temperature down before you call. It hides the reading your oncology team needs in order to decide how fast you must be seen.
Is Feeling Cold and Shivering During Radiation a Sign of Fever?
It can be, and that is the first thing to rule out. Shivering is how the body raises its own temperature, so chills often arrive before the thermometer catches up. Take a reading the moment the chill starts. During cancer treatment, 38°C (100.4°F) or above needs a call the same hour, not the next morning.
Measure it, do not guess it
A forehead that feels warm to a worried hand is not a measurement. Use a thermometer under the tongue or in the armpit, and write the number and the time down.
Read it again an hour later
A temperature that sits just below the threshold and stays there for an hour counts too. Two readings an hour apart tell your team far more than one.
Recognise a rigor for what it is
Shaking so hard that the bed or the chair moves is called a rigor. It is not simply feeling cold. A rigor needs a phone call even when the thermometer still reads normal.
Look for what comes with it
Chills with breathlessness, confusion, burning on passing urine, loose motions, or pain and redness around the treated area or a drip line move this straight to urgent.
Why the caution: radiation given alongside chemotherapy can lower the white cells that fight infection, so an infection can move faster than it otherwise would. If you are having blood tests through your course, what your blood counts mean during radiation explains what the team is watching for. This follows general NCCN and ASTRO patient-safety guidance and is not a diagnosis.
Did you know?
The NCCN treats a single reading of 38.3°C (101°F), or 38°C (100.4°F) that stays up for more than an hour, as the point at which someone on cancer treatment needs urgent assessment rather than a wait-and-see at home — because when white cell counts are low, an infection can advance faster than the symptoms suggest. Shivering usually starts before the thermometer moves, which is exactly why the chill itself is worth acting on.
Question 2 — is it anxiety?
Can Anxiety Cause Chills and Sweating During Radiation Treatment?
Yes, and it is not imagined. Adrenaline narrows the small blood vessels in the skin, so the hands and feet go cold and the palms go damp while the core stays warm. Anxiety chills build before the appointment and settle after it. What they never do is push the temperature up.
| What to compare | More like anxiety | More like infection |
|---|---|---|
| Temperature | Normal on every reading | 38°C (100.4°F) or above, or creeping up over an hour |
| When it starts | Before or during the session, or the night before a scan result | Any time, often waking you from sleep |
| How the skin feels | Cold hands and feet, damp palms, body warm underneath | Cold and clammy all over, or hot and flushed |
| How long it lasts | Settles within about an hour of leaving the centre | Keeps returning, or gets steadily worse through the day |
| What comes with it | Fast heartbeat, dry mouth, shallow breathing, a knot in the stomach | Aching, breathlessness, confusion, burning urine, loose motions, pain at the treated area |
| What to do | Tell the radiographers, sit down, slow the breathing, raise it at the weekly review | Call 1800 202 8726 or go to the nearest emergency department now |
Use the table in that order. Temperature is the first row for a reason. Anxiety is a fair explanation only once the thermometer has been read and is normal — never instead of reading it.
A racing heart alongside the chill is worth reading about separately: palpitations and a rapid heartbeat during radiation covers when that needs review in its own right.
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A Fever Is Not Something to Sleep On
Our radiation oncology team can tell you within minutes whether the chills you are describing need an emergency department tonight or a note for the weekly review.
Once fever is ruled out
What Else Makes You Feel Cold or Sweat During Radiation?
Plenty, and most of it is fixable. The treatment room itself is cold. Blood counts, thyroid function, hormone change, missed meals, pain and broken sleep all shift how you hold your temperature. None of these should be assumed until a fever has been excluded first.
The treatment room is genuinely cold
Rooms are kept cool and dry for the equipment. You lie still, on a hard couch, with the treated area uncovered. Ask the radiographers about a blanket over the rest of you.
Low blood counts
When chemotherapy runs alongside radiation, red cells can fall. Feeling cold, tired and breathless on stairs tends to arrive together, and a blood test settles it quickly.
An empty stomach
Early appointments, fasting instructions and a poor appetite leave blood sugar low. Cold, shaky and sweaty half an hour before a session is a common pattern.
The thyroid, after neck treatment
Radiation near the neck can make the thyroid gland underactive over months or years. Feeling cold all the time, with tiredness and dry skin, is worth a blood test.
Hormone change
Pelvic radiation can bring on an early menopause, and hormone-blocking treatment causes flushes and sweats too. These are hot sweats, not cold shivers.
Pain and broken sleep
Poorly controlled pain sets off sweating and shivering on its own, and disturbed nights make everything feel worse. Both are treatable once they are reported.
Dehydration
Low fluid intake on treatment days lowers blood pressure. Feeling cold, clammy and light-headed on standing often traces back to nothing more than that.
These symptoms are under-reported for a simple reason: patients assume feeling cold is too trivial to mention, so it stays unmentioned until the weekly review, or later. It is not trivial, and mentioning it costs nothing.
Question 3 — when does it need review?
When Do Chills or Sweating During Radiation Need Review?
Three speeds. Call now for a temperature of 38°C (100.4°F) or above, a rigor, or chills with breathlessness or confusion. Call the same day for daily sweats, drenched bedclothes, or a temperature sitting just under the threshold. Everything else goes on the list for the weekly review.
| What you are noticing | Usually expected | Call the same day | Call now or go to hospital |
|---|---|---|---|
| Feeling cold on the treatment couch | Cold for the few minutes of the session, warm again afterwards | Cold and shivery for hours after every session | With a temperature of 38°C (100.4°F) or above |
| Shaking chills (a rigor) | Nothing in this row is expected | Not applicable — do not wait a day for a rigor | Any shaking chill, even with a normal thermometer reading |
| Sweating at night | An occasional warm night, bedclothes dry by morning | Most nights, or sweats soaking through nightclothes | With a temperature, new lumps, or weight you have not tried to lose |
| Sweating with a racing heart | Brief, around an appointment, settling within the hour | Happening away from the centre, or several times a week | With chest pain, breathlessness or feeling about to black out |
| Feeling cold all the time | Cold on treatment days, normal in between | Every day for more than a week, with tiredness or dry skin | With a temperature, or with confusion or drowsiness |
| Chills with pain at the treated area or a drip line | Not applicable — this combination is never routine | Mild new tenderness, no fever and no redness | Redness, swelling, discharge or spreading pain — go now |
What not to do while you decide. Do not bring the temperature down before you have called, because it hides the reading. Do not start anything bought over the counter. Do not add to or stop a prescribed medicine on your own, and do not skip the next session without telling the team.
Genuinely unsure whether this counts? Call 1800 202 8726 and describe it. Being told it can wait costs one phone call.
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What Should You Do at Home, and What Should You Tell the Team?
Keep a written record, and keep warm. Two temperature readings an hour apart, the time the chills started, what else came with them, and what you have already taken. Bring that record to the call and to the appointment, rather than a summary from memory.
- Write the readings down with times — a page of numbers is worth more to your oncology team than any description of how hot you felt.
- Layer, do not overheat — blankets and warm drinks while you shiver, then something you can take off once the shivering stops.
- Keep drinking — unless you have been told otherwise, and unless a bladder-filling or bowel-prep instruction for your session says something different.
- Do not medicate the number away — nothing to bring the temperature down before the call, and nothing bought over the counter.
- Say it at the weekly review anyway — even the mild version. Feeling cold is the classic symptom people leave out because it sounds too small.
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Related reading on the symptoms nobody warns you about
Chills and sweats rarely arrive alone, and the quieter side effects are the ones most often left unmentioned until the weekly review:
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Common questions
Chills, Shivering and Sweating: Your Questions Answered
Is feeling cold and shivering during radiation therapy a sign of fever?
It can be, and that is the first thing to rule out. Shivering is the body's way of raising its own temperature, so chills often arrive before a thermometer shows anything. Take the temperature as soon as the chill starts, and take it again an hour later. During cancer treatment, a reading of 38°C (100.4°F) or above needs a call the same hour rather than the next morning. Shaking chills severe enough to rattle the bed, called a rigor, need a call even if the thermometer still reads normal. When blood counts are low an infection can move quickly, and NCCN guidance treats fever in this situation as urgent rather than something to watch at home.
Can anxiety cause chills and sweating during radiation treatment?
Yes. Anxiety is a genuine and common cause of feeling cold, shivery or clammy around a radiation session, and it is not imagined. Adrenaline narrows the small blood vessels in the skin, which makes the hands and feet feel cold and the palms damp while the core stays warm. Anxiety chills usually build before or during the appointment, settle within an hour of leaving, and arrive with a fast heartbeat, a dry mouth and shallow breathing. What they do not arrive with is a raised temperature. That is the dividing line. Check the temperature first, and only call it nerves once the thermometer is normal.
When should I call the hospital about chills or sweating during radiation?
Call straight away for a temperature of 38°C (100.4°F) or above, for shaking chills, for feeling cold and unwell with a racing pulse, or for chills that come with breathlessness, confusion, burning on passing urine, or pain and redness around the treated area or a drip line. Call the same day for repeated night sweats, for feeling cold every day for more than a week, for sweats that soak the bedclothes, or for a temperature that keeps sitting just below 38°C. Anything milder can wait for the weekly review, but still mention it. Do not take anything to bring a temperature down before you call, because it hides the reading the team needs.
Why do I feel cold in the radiation treatment room?
Partly because the room genuinely is cold. Treatment rooms are kept cool and dry to protect the equipment, you lie still on a hard couch with the treated area uncovered, and a session takes several minutes. Add nerves, an early appointment and often an empty stomach, and shivering on the couch is common. It is not a sign that the beam is doing something to you. Tell the radiographers, because a blanket over the untreated parts of you is usually possible, as long as it does not disturb your position or the marks used to set you up.
What causes night sweats during radiation therapy?
Several things, and they are worth separating. An infection is the first to rule out. Hormone change is the next most common cause, particularly after pelvic radiation, which can bring on an early menopause, and in patients on hormone-blocking treatment. Radiation near the neck can affect the thyroid gland over months and change how you regulate temperature. Pain, broken sleep and anxiety all add to it. Drenching night sweats that happen most nights, especially with a temperature, weight loss or new lumps, should be reported rather than absorbed into the general tiredness of treatment.
Should I take anything at home for chills during radiation treatment?
Not before you have taken the temperature and spoken to the team. Anything that brings a temperature down also hides it, and that reading is the single most useful piece of information your oncology team has when deciding how fast you need to be seen. Do not start anything bought over the counter, and do not add or stop a prescribed medicine on your own. What helps safely is warmth, layers you can remove, fluids unless you have been told otherwise, and a written note of the times and readings. If something is needed, your team will prescribe it.
This page is general health information about telling an expected chill or sweat apart from a fever that needs urgent review during radiation treatment. It is not a diagnosis and cannot replace assessment by your own team. If the temperature is 38°C (100.4°F) or above, if there is a shaking chill, or if chills come with breathlessness or confusion, treat it as urgent now — call 1800 202 8726 or go to the nearest emergency department. Radiotherapy is delivered at NABH-accredited partner centres; CION Cancer Clinics coordinates your treatment plan, your oncology team and your care throughout.