Medical Oncologist
Side effect monitoring
When to Call Your Oncologist — Side Effects That Cannot Wait
Most side effects during cancer treatment are expected and manageable. A few are not. Knowing the difference — and knowing to call rather than wait — is the one piece of information that changes outcomes most.
Medically reviewed by Dr. C. Raghavendra Reddy, Medical Oncologist, MBBS (Gold Medal) · DNB · DM (Medical Oncology, Gold Medal) · Last reviewed August 2026
- Fever means call now — During chemotherapy, any new fever is a potential sign of serious infection and needs same-day assessment — never wait overnight.
- Tiredness is expected — Fatigue and nausea in the first days after treatment are normal. Not every symptom needs urgent action.
- Uncertainty is a reason to call — If you are not sure whether something is serious, call today. That is exactly what your team's helpline is for.
- Out-of-hours symptoms count — Serious symptoms do not wait for clinic hours. Your team has a process for calls at night and on weekends.
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Call your oncologist today if you have a new fever, cannot keep fluids down, have chest pain, feel confused, or notice unexpected bleeding. NCCN and ASCO guidance treats fever during chemotherapy as needing same-day emergency assessment, not a wait-and-see approach. For anything else that worries you, call rather than wait — your team would rather hear from you early.
If a symptom below applies to you, do not wait for a callback. Call 1800-202-8726 or go to your nearest emergency department.
What is normal in each week of treatment, and when should you call?
| Period | Commonly expected | Call your team today |
|---|---|---|
| First 24-48 hours | Nausea, mild headache, tiredness | Fever, chest pain, vomiting you cannot control at all |
| Days 3-7 | Fatigue, reduced appetite, mouth soreness beginning | Fever at any point, new or unexpected bleeding, diarrhoea that worsens each day |
| Week 2 — days 7-14 | Fatigue often at its worst, possible hair loss beginning | Fever or chills, redness or warmth around a line site, any sign of infection |
| Weeks 3-4 | Energy and appetite gradually returning | Any new symptom appearing now, or fever returning unexpectedly |
| Typically starts | Fatigue and nausea begin within the first day or two and peak in week 1-2 for most chemotherapy | Serious infections can develop from day 7 onward; immunotherapy reactions may appear weeks to months after starting |
When should you call today rather than go straight to emergency?
Most symptoms that worry you belong in a same-day call, not an emergency department. Call your team if you have a fever that is new but not yet severe, diarrhoea that has clearly worsened over 24 hours, mouth sores making eating impossible, or pain that feels different from your usual ache.
Your team can assess on the phone and tell you whether to come in or go to emergency. That call takes the guesswork away.
If you cannot reach anyone and you are genuinely worried, go to emergency rather than wait. Always choose action over uncertainty.
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Dr. C. Raghavendra Reddy
MBBS(Gold Medal), DNB(General Medicine), DM(Medical Oncology)(Gold Medal)
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Dr. Bharati Devi Gorantla
MBBS, MD(General Medicine), DM(Medical Oncology)(Adyar,Chennai), ECMO, MRCP SCE(UK)
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MBBS, MD (General Medicine), DrNB (Medical Oncology), ECMO, MRCP SCE (Medical Oncology) (UK)
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MBBS (AIIMS), MS (Surgery) (AIIMS), DNB (Surgical Oncology), MRCS (Edinburgh)
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Dr. Vinay Mamidala
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What do you say when you call your oncology team?
When you call, your team needs three things quickly: what the symptom is, when it started, and whether it is getting worse or staying the same.
Write these down before you call if you can. A clear account of the change — 'I felt fine yesterday but today I cannot keep water down' — helps your team make the right decision in a short call.
Tell them everything you have taken, including any herbal preparation or home remedy, because some interact with treatment in ways that affect how a symptom should be read.
Did you know?
ASCO clinical guidance on chemotherapy toxicity identifies delayed reporting of fever as one of the most common preventable contributors to serious complications during treatment.
The difference between an urgent call and a hospital admission is often a matter of hours. Your team would rather reassure you on a phone call than see you in emergency two days later.
Source: ASCO clinical guidance on cancer treatment toxicity management
What families ask most about calling the team
What if I am not sure whether it is serious enough to call?
Call anyway. The oncology helpline is designed for exactly this — you do not need to diagnose yourself before picking up the phone. You will be asked a few quick questions, and someone trained to assess treatment side effects will tell you what to do next. Hesitating because you are not sure is the one thing that leads to delays, and delays are what change manageable reactions into serious ones. Uncertainty is always a reason to call, not a reason to wait.
What if it is the middle of the night or a weekend?
Your team has an out-of-hours number for this reason. Ask your oncologist for it at your next visit, and keep it somewhere you can find at 2am — written down, not just in a phone you cannot unlock. If you cannot reach anyone and something is worrying you, go to the nearest emergency department and tell them you are on active cancer treatment. They will prioritise accordingly. Do not wait until Monday morning if a symptom is worsening tonight.
Will the team think I am overreacting?
No oncologist or oncology nurse has ever been frustrated by a patient who called too early. Concern comes in the other direction — from patients who waited too long. Your treating team has built their practice around early reporting, and a call that ends in reassurance is a good outcome for everyone. Please call as often as you need to. That is what the helpline is for.
Can I take paracetamol to bring the fever down before calling?
Do not take paracetamol before you call if you are on chemotherapy and you have developed a new fever. It can reduce your temperature and mask a sign your team needs to see, which changes how urgently they are able to respond. Call first. If your team has already told you that paracetamol is appropriate for you in a specific situation, follow that guidance — but if you are not sure, the default is always to call before taking anything.
What about symptoms that appear after the last treatment session ends?
Side effects do not always appear during the infusion or in the hours that follow. Chemotherapy effects on bone marrow can peak several days later, which is why serious infections are most common in week two. Immunotherapy reactions can appear weeks to months after the last dose. If a new or worsening symptom appears after your most recent session, treat it the same way you would during treatment: check the red flags on this page, and if you are unsure, call your team rather than assuming it will settle on its own.
Explore 108 more Side Effects, Emergencies & Daily Living topics
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- Side Effect Timeline: What Happens in Week 1, Month 1 and Month 6
- Targeted Therapy Side Effects: The Complete List by Drug Class
- Understanding Side Effect Grades 1 to 4 (In Plain Language)
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- I Accidentally Took a Double Dose: How Serious Is It?
- I Missed a Dose of My Targeted Therapy: What Should I Do?
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- Managing a Household Routine Around Your Dosing Schedule
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- Safe Disposal of Unused Cancer Medicines
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- Smoking and Targeted Therapy: How It Changes Your Drug Levels
- Travelling With Cancer Tablets: Flights, Security and Storage
Emergency & Red-Flag Triage
- Chest Pain or Palpitations During Cancer Treatment
- Emergency Contact Card: What to Keep in Your Wallet
- Fever Above 100.4F on Cancer Treatment: The 1-Hour Rule
- Heavy Bleeding, Blood in Vomit or Black Stools
- Not Passing Urine or Sudden Swelling All Over
- Severe Rash Spreading Rapidly With Mouth or Eye Involvement
- Sudden Breathlessness on Cancer Tablets: Go to Emergency or Wait?
- Sudden Confusion, Seizure or Weakness on One Side
- Sudden Severe Abdominal Pain: Ruling Out Perforation
- Sudden Vision Loss or Double Vision: What to Do Right Now
- Swollen, Painful Leg: Recognising a Blood Clot
- Uncontrolled Diarrhoea: The 6-Stool Rule Every Patient Should Know
- What to Tell an ER Doctor Who Doesn't Know Your Cancer Drug
- Yellow Eyes, Dark Urine or Severe Right-Sided Pain
Food, Drug & Supplement Interactions
- Antacids and Acidity Tablets Can Block Your Cancer Drug
- Anti-Nausea and Anti-Acidity Drugs That Prolong QT
- Anti-TB Treatment and Targeted Therapy: A Dangerous Combination
- Antibiotics and Antifungals That Interfere With Cancer Drugs
- Ayurvedic and Herbal Medicines With Targeted Therapy: The Real Risks
- Blood Thinners and Targeted Therapy: Managing the Bleeding Risk
- Contraceptive Pills and Hormone Medicines With Cancer Drugs
- Diabetes and Blood Pressure Medicines With Targeted Therapy
- Grapefruit, Pomegranate and Starfruit: Why They're Banned on Many Cancer Drugs
- Green Tea, Coffee and Caffeine on Targeted Therapy
- Homeopathy Alongside Targeted Therapy: What You Should Know
- How to Check Any New Medicine Against Your Cancer Drug
- Painkillers: Which Ones Are Safe on Targeted Therapy?
- Protein Powders and Immunity Boosters: Helpful or Harmful?
- Statins and Cholesterol Medicines During Cancer Treatment
- The Complete Do-Not-Take List for Common Targeted Therapy Drugs
- Turmeric, Ashwagandha, Giloy and Wheatgrass During Cancer Treatment
- Vaccines and Antivirals During Targeted Therapy
- Vitamin, Calcium and Iron Supplements During Treatment
Side Effects - Symptom-Specific Deep Dives
- Abdominal Pain on Targeted Therapy: When to Worry
- Acne-Like Rash on EGFR Inhibitors: Why It Happens and How to Treat It
- Anaemia and Low Haemoglobin During Targeted Therapy
- Blood Clots and Stroke Risk on Targeted Therapy
- Blurred Vision and Eye Problems on Cancer Drugs
- Brain Fog and Memory Problems During Treatment
- Breathlessness and Cough on Targeted Therapy: Ruling Out ILD
- Constipation During Targeted Therapy
- Diarrhoea on Targeted Therapy: How to Control It at Home
- Dry Eyes and Light Sensitivity During Treatment
- Extreme Fatigue on Targeted Therapy: Causes and What Helps
- Extremely Dry, Cracking Skin on Cancer Tablets
- Fever During Targeted Therapy: Home Care vs Emergency
- Hair Thinning, Curling and Colour Change on Targeted Therapy
- Hand-Foot Skin Reaction: Prevention and Relief
- Headaches and Dizziness on Targeted Therapy
- Heart Function Drop (Low Ejection Fraction) on Targeted Therapy
- High Blood Pressure Caused by Cancer Drugs
- High Blood Sugar on PI3K and mTOR Inhibitors
- Infusion Reactions: What Happens and How They're Managed
- Interstitial Lung Disease (ILD): The Side Effect You Must Not Ignore
- Itching That Won't Stop on Targeted Therapy
- Kidney Function Changes on Targeted Therapy
- Loss of Appetite and Weight Loss During Targeted Therapy
- Low Magnesium and Electrolyte Problems on Anti-EGFR Antibodies
- Low Platelets on PARP Inhibitors and TKIs
- Low White Cells and Infection Risk on Targeted Therapy
- Mouth Ulcers and Mucositis: Practical Relief
- Muscle Cramps and Joint Pain on Cancer Drugs
- Nausea and Vomiting on Oral Cancer Drugs
- Osteonecrosis of the Jaw: Prevention During Bone-Targeted Treatment
- Paronychia and Nail Changes on Targeted Therapy
- Peripheral Neuropathy: Tingling and Numbness in Hands and Feet
- Protein in Urine (Proteinuria) During Treatment
- QT Prolongation: What It Means on Your ECG Report
- Raised Liver Enzymes (SGPT/SGOT) on Targeted Therapy
- Secondary Cancers After Long-Term PARP Inhibitor Use
- Severe Rash With Fever or Blistering: A Medical Emergency
- Skin Darkening, Depigmentation and Pigment Changes
- Slow Heart Rate and Dizziness on Certain TKIs
- Sun Sensitivity and Photosensitivity on Cancer Drugs
- Swallowing Difficulty and Reflux on Cancer Tablets
- Swelling of Face, Legs and Around the Eyes
- Taste Changes and Metallic Mouth on Cancer Drugs
- Tumour Lysis Syndrome: A Rare but Serious Early Complication
- Underactive Thyroid (Hypothyroidism) Caused by Cancer Drugs
- Unusual Bleeding or Bruising on Cancer Drugs
- Voice Changes and Hoarseness on Targeted Therapy
- Weight Gain During Long-Term Targeted Therapy
- When Diarrhoea Becomes an Emergency: The Rule You Must Know
- Wound Healing Problems on Antiangiogenic Drugs
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Common questions
Frequently asked questions
Is it normal to feel worse in week two than in week one?
Yes, and it surprises many people. Fatigue and some effects of chemotherapy often peak in the second week of a cycle rather than immediately after the infusion, because some effects on the body — particularly on blood cell production — take several days to appear. The important distinction is whether the worsening involves fever, signs of infection, or unexpected bleeding alongside the fatigue. Fatigue alone in week two is expected; fever or signs of infection in week two needs a same-day call.
What is febrile neutropenia and why does my team keep mentioning it?
Febrile neutropenia means fever combined with a very low white blood cell count — a condition many chemotherapy drugs can cause. White blood cells are the body's main defence against infection, and when the count drops, even a minor infection can become serious rapidly. This is why NCCN and ASCO treat fever during chemotherapy as urgent rather than wait-and-see. Your team may have given you a card explaining what to do if you develop a fever — if so, follow it exactly and do not modify the plan without calling first.
What symptoms can I safely monitor at home without calling?
Mild fatigue, a reduced appetite, loose stools that are not worsening day on day, mild mouth soreness, and gradual hair thinning are all expected effects that do not usually need a same-day call. The question to ask yourself is whether the symptom is staying the same, improving, or getting worse. Stable or improving means monitor it and mention it at your next appointment. Worsening — or any symptom matching the red flags on this page — means call or go to emergency.
My family member had very different side effects on the same treatment. Is that normal?
Yes. Two people on the same treatment can have very different experiences. Side effects depend on the cancer type, the specific medicines and doses, age, general health, and factors that are not fully predictable in advance. What matters is not matching another person's experience but knowing your own baseline and reporting changes from it. Use the week-by-week table on this page as a guide rather than someone else's account.
Should I keep a symptom diary during treatment?
Yes, and most oncology teams recommend it. A brief daily note — how you felt, what was new, what you ate and drank, any medicines you took — takes two minutes and makes every call to your team more useful. When you can describe a change specifically — when it started, whether it is getting worse, what makes it better or worse — your team can assess it accurately in a short call. A diary also helps you spot a pattern before it becomes a problem.