Herceptin (trastuzumab)
Targeted therapy (HER2 antibody) · Used for: Breast cancer
💉 Given by IV or injection · Targeted therapy (HER2 antibody)
Cliff notes
What it is: Targeted therapy (HER2 antibody).
How it's given: An IV infusion, usually every 1 or 3 weeks. Biosimilar versions and an under-the-skin version also exist.
How it works: Some breast cancers make too much of a protein called HER2, which drives their growth. A test on your tumor shows if yours is HER2-positive. Herceptin attaches to HER2 and blocks it, and it helps your immune system target those cells.
Common side effects and what helps at home
| Side effect | What can help |
|---|---|
| Infusion reactions (fever, chills) | Most happen with the first dose. Your team watches you. Chills and fever are among the most common side effects. |
| Tiredness | Rest when needed. |
| Diarrhea | Fluids and bland food. |
| Headache, nausea | Ask what you can take. |
Not everyone gets these. Your team may suggest other ways to manage them.
Call your care team now if you have:
- Shortness of breath, swelling in your legs or feet, fast heartbeat or sudden weight gain (possible heart problems)
- Trouble breathing, wheezing or swelling during or after an infusion
- Fever of 100.4°F (38°C) or higher
- New cough, wheezing or shortness of breath (possible lung problems; this is in the label's boxed warning)
- You are or might be pregnant. Herceptin can harm an unborn baby, so use birth control during treatment and for 7 months after the last dose
Call 911 for trouble breathing, chest pain or signs of stroke.
🗓 What to expect
1️⃣ Before you start
- Ask your team for a written schedule and an after-hours phone number.
- A heart test (often an echocardiogram) to check your heart's pumping.
- Bring a list of all your medicines and supplements.
2️⃣ During each infusion
- You'll get the medicine through an IV in a clinic; nurses check you during the infusion.
- Tell the nurse right away about chills, itching, flushing or trouble breathing.
- Bring a snack, water and something to pass the time.
3️⃣ Between doses
- Watch for the side effects below and use the checklist.
- Keep up with blood tests and visits.
- Call your team for anything in the red box.
✅ Side-effect checklist
Print this and check off what you notice so you can tell your team.
| Side effect | Noticed? | Notes for my team |
|---|---|---|
| Infusion reactions (fever, chills) | ☐ | |
| Tiredness | ☐ | |
| Diarrhea | ☐ | |
| Headache, nausea | ☐ |
Help paying for Herceptin
Official manufacturer program:
- Genentech Patient Support Services: Benefits checks and copay help; the Genentech Patient Foundation for uninsured or low-income patients.
Copay cards are usually only for people with commercial (job or marketplace) insurance. If you have Medicare or Medicaid, look at free-drug programs and these independent foundations:
- PAN Foundation: Copays and coinsurance, including for people with Medicare, when a disease fund is open.
- HealthWell Foundation: Grants for copays, deductibles and premiums when a fund is open.
- CancerCare Co-Payment Assistance Foundation: Help with treatment copays for insured people under income limits.
- Good Days: Copay help and some travel costs.
- NeedyMeds: Free database of assistance programs, open to anyone.
📋 Medicare: Medicare Part B usually covers drugs given by infusion in a doctor's office or hospital outpatient clinic. You typically pay 20% after the Part B deductible. See Medicare and your cancer drugs.
More: Our guide to paying for cancer treatment.
▶ Watch
Videos open on YouTube and are made by the channels named. We don't host them.
❓ Questions to ask your doctor
- What is the goal of this treatment for me?
- How will we know if it's working?
- Which side effects should I call about right away, and what number do I call after hours?
- Which medicines, vitamins or supplements should I avoid?
- Will this affect my ability to work, drive or care for my family?
- What will this cost me, and who can help me with coverage?
Support groups
- Susan G. Komen: Breast care helpline, treatment assistance and education
- Living Beyond Breast Cancer: Helpline, peer support and programs for metastatic breast cancer
- CancerCare: Free counseling, support groups and financial help
- Cancer Support Community: Support groups, a helpline and the MyLifeLine online community
Common questions
Why do I need heart tests on Herceptin?
Herceptin can weaken the heart muscle. Your team checks your heart (often with an echocardiogram) before and during treatment.
Does Herceptin cause hair loss?
Herceptin alone usually doesn't. Chemo given with it often does.
📄 The official FDA label for Herceptin, including its patient information section, is on DailyMed.
Written by the Cancer Side Effects Guide team from FDA labels and leading cancer centers. Not medical advice. · Last updated: October 15, 2026 · How we write