Chemotherapy side effects can start from the very first session, but each one has its own timing: nausea in the first 24 hours or over the following days, up to about a week [3], and tiredness mostly in the few days after each session [4]. With many chemotherapy medicines, white blood cells fall to their lowest about one to two weeks after the infusion, and the risk of infection is higher on those days [1, 7, 8, 9]; hair loss usually starts 2 to 3 weeks after treatment begins [1]. Most side effects ease before the next session or after treatment ends, but some, such as tingling and numbness in the hands and feet, may build up with each cycle and last for months [1, 8, 11].
Key points
- No two people are exactly alike: which side effects you have, and how strong they are, depends on the type and dose of your medicines, the type of cancer and how healthy you were before treatment [2].
- The hardest days are usually the first few days after each session: delayed nausea, the worst tiredness and, if you have been given a steroid, poor sleep [3, 4, 6].
- About one to two weeks after each session is the most sensitive time for infection: report a temperature of 38°C or higher straight away [1, 7, 8].
- With some medicines, tingling and numbness in the hands and feet build up with each cycle; mention it early so the dose or schedule can be adjusted before it becomes serious [8, 10].
Chemo side effects timeline: day by day in a 3-week cycle
This table shows the usual pattern of a chemotherapy cycle that repeats every 3 weeks. Your schedule may be different; ask your team which days are most sensitive with your medicines, and mark them in the chemotherapy calendar.
| When | What may happen | What should I do? |
|---|---|---|
| Infusion day (day 1) | Acute nausea in the first 24 hours [3]; pain or burning where the needle goes in [1]; with oxaliplatin, tingling or sensitivity to cold from a few hours to 2 days afterwards [10] | Take your anti-sickness medicine as scheduled and have someone take you home [1, 2]; tell the nurse at once about pain or burning at the needle site [1]; with oxaliplatin, avoid cold drinks, ice and contact of the skin with cold [10] |
| Days 2 to 5 | Delayed nausea, which may last up to about a week [3]; the worst tiredness [4]; if you have been given a steroid (dexamethasone): poor sleep, heartburn, restlessness and a bigger appetite [6]; sometimes flu-like symptoms for 1 to 3 days [1] | Keep taking your anti-sickness medicine in the days after the session, as your doctor prescribed [1]; plan rest and help with household tasks on the day of treatment and the day after [2]; take short rests of 10 to 15 minutes [1] |
| Days 7 to 14 | The lowest white blood cell count and the highest risk of infection with many medicines [7, 8, 9]; mouth sores: first signs from day 3 or 4, worst on days 7 to 14 [5] | Take your temperature once a day [1]; wash your hands often and keep away from people who are ill and from crowds [1]; check your mouth every day and care for it with a very soft toothbrush and an alcohol-free mouthwash [1] |
| 2 to 3 weeks after treatment starts | Hair loss begins with medicines that cause it; it takes about a week for all the hair to fall out [1] | If you wish, cut your hair short before it falls out; this may give you a greater sense of control [1] |
| Days 15 to 21 | Blood counts recover; with doxorubicin, for example, usually by day 21 [7]; tiredness eases before the next session [4] | A blood test is done before the next session; if your counts are still low or a side effect is severe, your doctor may delay the session [1, 2] |
This pattern is approximate and varies from one medicine to another and from person to person; not everyone gets all of these side effects.
Side effects of your first chemo treatment
Side effects can begin with the very first session: nausea on the day or a few days later [3], tiredness over the following days [4], and lower blood counts about one to two weeks later [7, 8, 9]. Hair loss, however, starts a few weeks later [1], and some side effects, such as tingling in the hands and feet, appear after more sessions; with paclitaxel, nerve symptoms were seen in about 1 in 4 people after the first cycle and in a third to a half of patients in later cycles [8].
The first session shows your team how your body reacts. Tell them about any side effect; if your anti-sickness medicine does not work well, your doctor can prescribe a different one [1]. To prepare, read: Your first chemotherapy session: what to expect
Do chemo side effects get worse with each cycle?
- Tingling and numbness in the hands and feet (neuropathy): with some medicines, such as paclitaxel and oxaliplatin, it becomes more common the more cycles you have [8, 10]. With oxaliplatin there are two kinds: a short-lived kind that comes on a few hours to 2 days after each session, is made worse by cold and goes away within 2 weeks; and a lasting kind that usually appears after several cycles [10]. If the tingling persists, your doctor may lower the dose or stop the medicine [10]. Read more: Numbness and tingling in the hands and feet (neuropathy).
- Tiredness: in each cycle it is worst a few days after the session and eases before the next one [4]. In one study, tiredness was at its highest halfway through the course of chemotherapy and had still not quite returned to normal 30 days after the last session [4]. Read more: Cancer-related fatigue.
- Low blood counts: with some medicines, such as paclitaxel, they did not get worse as cycles were repeated [8]; a blood test before each cycle checks this [1].
- Nausea before a session: if you had nausea at earlier sessions, the smells, sounds or sight of the treatment room may bring on nausea before the next session [3]. Tell your doctor; a different medicine can help [1]. Read more: Nausea and vomiting during cancer treatment.
Weekly, every 2 weeks or every 3 weeks: how does the pattern of side effects differ?
Chemo every 3 weeks: the first few days of each cycle are usually the days of nausea and tiredness [3, 4], blood counts are lowest around the second week, and by the third week the body recovers before the next session [7].
Weekly or every 2 weeks: the sessions are closer together, so the sensitive days of each cycle are closer together too. In a large study in breast cancer, weekly paclitaxel gave better treatment results than paclitaxel every 3 weeks, but tingling and numbness in the hands and feet were a little more common [12].
With chemotherapy tablets taken every day, the pattern of side effects depends on the schedule of that medicine; ask your doctor or pharmacist. To read about the number of cycles: How many chemotherapy sessions will I need?
How long do chemo side effects last after the last session?
Most side effects go away after chemotherapy ends, but sometimes this takes months or even years [1].
| Side effect | When does it usually get better? |
|---|---|
| Nausea and vomiting | Delayed nausea may last up to about a week after a session [3] |
| Mouth sores | Most mouth problems get better a few days after chemotherapy ends [1, 5] |
| Hair loss | Hair almost always grows back 2 to 3 months later; at first it may be thinner, curlier or a different colour [1] |
| Tiredness | It gets better after treatment, but in some people a little may remain for months or years [4] |
| Tingling and numbness in the hands and feet | In a large review, about 7 in 10 people had it in the first month after chemotherapy and about 3 in 10 at 6 months or later [11]; many nerve problems get better within a year, but some are permanent [1] |
| Late effects | Damage to the heart, lungs, nerves, kidneys or fertility is sometimes permanent, and some medicines can cause a second cancer years later [1] |
Ask your doctor about the chance of long-term side effects from your own medicines.
When should I call my doctor?
Call your treatment team straight away in these situations, even at night or at the weekend [1]:
- A temperature of 38°C or higher (or whatever temperature your team has told you), chills or sweats, especially one to two weeks after a session; call before taking any medicine that lowers fever, even paracetamol (acetaminophen) or ibuprofen [1, 7]
- Cough, burning or frequent urination, or redness and swelling around a port or catheter [1]
- Vomiting for more than a day, or bringing up everything you drink [1]
- Diarrhoea for more than 24 hours, or diarrhoea with pain and cramps [1]
- Sores, white patches or infection in the mouth [1]
- Unexplained bruising, bleeding from the nose or gums, or tiny red spots on the skin [1]
- Tingling or numbness that makes writing, doing up buttons, swallowing or walking difficult [10]
If you suddenly feel very unwell, for example with severe breathlessness, confusion or severe weakness with a fever, call your local emergency number. Read more: Fever and warning signs during chemotherapy and Low blood counts and preventing infection.
Frequently asked questions
After which chemo session do side effects start?
How many days do chemo side effects last?
It depends on the side effect: delayed nausea may last up to about a week after a session [3], tiredness is worst a few days after the session and eases before the next one [4], and blood counts usually recover by the next session; with doxorubicin, for example, by about day 21 [7].
What are the worst days after chemo treatment?
Why can't I sleep after chemotherapy, and why am I so hungry?
The steroid dexamethasone, given to prevent nausea, can cause poor sleep, heartburn, restlessness, a bigger appetite and weight gain in the week after chemotherapy; in one study, almost half of patients had moderate to severe sleep problems [6]. Tell your team, and do not stop any medicine on your own.
If I had fewer side effects this cycle, does it mean the medicine is not working?
No. Side effects have nothing to do with how well chemotherapy is fighting the cancer; whether treatment is working is measured with examinations, tests and scans [2].
Timing of side effects in drug labels and studies (for doctors)
For physicians
- Neutrophil nadir (FDA labels): doxorubicin every 21 days: nadir on days 10–14, with recovery usually by day 21 [7]. Paclitaxel: median nadir at day 11; neutropenia did not increase with cumulative exposure [8]. Docetaxel: median time to nadir 7 days, and median duration of severe neutropenia (below 500 cells/mm³) 7 days [9]. Assessing fever and neutropenia: Fever and neutropenia and MASCC score.
- Neuropathy: paclitaxel: peripheral neuropathy in 60% of all patients (3% severe), more frequent with increasing cumulative dose; neurological symptoms in 27% after the first course and in 34% to 51% from courses 2 to 10 [8]. Oxaliplatin: acute neuropathy within hours to 2 days of a dose, resolving within 14 days, triggered by cold and recurring with further doses (in 56% of patients given it with fluorouracil/leucovorin; about 30% in any single cycle); persistent delayed neuropathy (more than 14 days) in 48%; median time to grade 3 sensory neuropathy 9 cycles in adjuvant treatment and 6 cycles in previously treated advanced colorectal cancer; reduce the dose or stop permanently for persistent symptoms [10]. In E1199, grade 2–4 neuropathy occurred in 27% with weekly paclitaxel vs 20% with paclitaxel every 3 weeks, together with improved disease-free survival (OR 1.27) and overall survival (OR 1.32) [12]. CIPN prevalence in a meta-analysis of 31 studies (4,179 patients): 68.1% in the first month after chemotherapy, 60.0% at 3 months and 30.0% at 6 months or more [11].
- Nausea: acute within 24 hours of the start of treatment and delayed 1 to 7 days after treatment [3]; choosing prophylaxis: Choosing an antiemetic regimen.
- Dexamethasone: in 60 patients receiving moderately emetogenic chemotherapy, moderate to severe problems in the week after chemotherapy: insomnia 45%, indigestion or epigastric discomfort 27%, agitation 27%, increased appetite 19%, weight gain 16% and acne 15% [6].
- Mucositis: with cyclic chemotherapy, first signs 3–4 days after the infusion, ulceration from the second week with peak severity on days 7–14, and spontaneous healing in the week after chemotherapy stops [5].
- Fatigue: with cyclic regimens, fatigue peaks in the days after treatment and then declines until the next cycle [4].
References
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Numbers in the text, such as [1], refer to these sources. Sources with a “Study card” button are summarised in the site’s evidence library.
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This page is based on reputable scientific sources and was last updated on 28 October 2026. The content of this website is for educational and informational purposes only and does not replace consultation, diagnosis or treatment by a specialist physician. Consult your treating physician about any treatment decision.
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