Chemotherapy side effects vary by drug, but most patients experience a predictable pattern around each infusion. Knowing what's typical (and what's not) takes a lot of fear out of the process.
Day of infusion (day 1): most patients feel close to normal. The drugs haven't fully kicked in yet. You'll usually receive anti-nausea medication before and after the infusion.
Days 2–4: peak side effects for most regimens. Common: fatigue, nausea, taste changes, mild headache. Anti-nausea medications work best when taken on schedule, not as needed.
Days 5–10: lowest blood counts (the nadir). You'll feel tired and are more vulnerable to infection. Avoid crowds and sick contacts. Your team will check labs around this point.
Days 11–21: counts recover and energy returns. Most patients feel best in the few days before the next infusion. Hair loss, if it occurs, typically starts around days 14–21 of the first cycle.
Side effects to manage at home: mild nausea, fatigue, constipation or diarrhea, mouth sores, dry skin, taste changes, mild numbness in fingers and toes (peripheral neuropathy).
Call the oncology team right away for: fever ≥100.4°F (38°C) — this is a medical emergency in chemo patients; uncontrolled vomiting or diarrhea (more than 24 hours); shortness of breath; chest pain; new or worsening numbness or weakness; signs of bleeding (unusual bruising, blood in urine/stool, severe nosebleeds); severe mouth sores that prevent eating or drinking; rash, hives, or facial swelling.
Most cancer centers, including Keck Medicine USC Newport Beach, have a 24/7 oncology nurse line. Save the number in your phone before treatment starts. Don't try to wait until morning if something feels seriously wrong — early intervention prevents hospitalizations.
Long-term: most acute side effects resolve within weeks of completing chemotherapy. Some — neuropathy, fatigue, cognitive changes ('chemo brain') — can linger for months or longer. Cancer survivorship clinics help manage these.