Medical Oncologist
Medicines
Missed a dose of trastuzumab emtansine? What to do
Trastuzumab emtansine is given as a drip in hospital every three weeks, so a missed dose usually means a missed appointment. The general guidance is to give the dose as soon as possible, not to wait for the next planned date, and then to count future cycles from the new date. This page explains what to do and what to expect.
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Medically reviewed by Dr. Naresh GunduConsultant Medical Oncologist · MBBS, DNB (Internal Medicine), DM (Medical Oncology, AIIMS) · last reviewed September 2026, next review due September 2027
On this page
- What should you do if a dose of trastuzumab emtansine is missed?
- What to do when an appointment is missed
- Different reasons, different responses
- The vocabulary, in plain language
- Honest limits of what is known
- Missed doses during the fourteen-cycle course
- Missed doses when treatment is ongoing
- What people assume about missed doses
- Common questions about missed T-DM1 doses
The short answer
What should you do if a dose of trastuzumab emtansine is missed?
Trastuzumab emtansine, also called T-DM1 or Kadcyla, is given as a drip in a hospital day-care unit, usually once every three weeks. Because you do not take it at home, a missed dose really means a missed or postponed appointment. That might happen because of illness, travel, a festival, a family emergency, a problem with insurance approval, or simply confusion over dates. The general guidance in the product information is clear: if a planned dose is missed, it should be given as soon as possible, rather than waiting until the next date that was originally planned. The schedule is then reset, so the following doses are again spaced three weeks apart from the new date. You do not receive a double dose to make up for the gap. The dose given is usually the one you last had and managed well. A short delay of a few days is common and is unlikely to matter much. Longer gaps are less well studied, so it is best to rearrange quickly. It is also important to know the difference between a missed dose and a planned delay. Your team may deliberately postpone a cycle if your platelets are low, your liver tests have risen, or your heart scan has changed. That is part of safe treatment, not a mistake. Whatever the reason, contact your oncology team as soon as you know a dose has been or will be missed.
Rebook as soon as you can
The missed dose is given at the earliest suitable date, not saved for the next planned one.
No double doses
The dose is not increased to make up for lost time. The schedule simply moves forward.
Planned delays are different
A delay your team chooses because of test results is a safety step, not a missed dose.
This page gives general information only. Your own oncology team decides when and how a delayed dose is given.Four practical steps
What to do when an appointment is missed
A calm, quick response keeps your treatment on track.
Tell your team the same day
Contact the day-care unit or your oncologist's office and explain what happened, even if you are unsure of a new date yet.
Mention any symptoms
If you missed the appointment because you felt unwell, describe your symptoms. You may need tests before the dose is given.
Fever, bleeding or yellow skin need urgent advice, not just a new date.Get the blood tests done
Your platelet count and liver tests are usually checked before each dose, including a rescheduled one.
Update your calendar
Future cycles move forward from the new date. Write them down so the next ones are not missed.
Worth noting down
- The new treatment date
- The date of your next heart scan
- How many cycles remain
Common situations
Different reasons, different responses
Situation
What usually happens
You forgot or mixed up the date
The dose is rebooked for the earliest available day, then the schedule resets
You had a cold, fever or infection
Your team checks you first and may wait until you recover
Your platelets or liver tests were abnormal
A planned delay, sometimes followed by a lower dose
Insurance approval was late
Tell your team early; they may help with paperwork to limit the gap
You need surgery or dental work
Timing is planned between your oncologist and the other doctor
Words you will hear
The vocabulary, in plain language
- Cycle
- One treatment followed by a three-week gap before the next.
- Dose delay
- Postponing a treatment, either by choice of your team or because an appointment was missed.
- Dose reduction
- Giving a lower dose from then on, usually because of side effects.
- Schedule reset
- Counting the next three-week gap from the date the delayed dose was actually given.
- Infusion rate
- How quickly the drip runs. Later doses usually run faster than the first if you coped well.
- Pre-treatment bloods
- Blood tests, including platelets and liver tests, checked before a dose goes ahead.
Talk to our team
Have a question about your situation?
Call the helpline or leave your details, and someone will help you arrange a consultation at the CION centre nearest you. One helpline serves every CION centre.
Call 1800 202 8726
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Being straight with you
Honest limits of what is known
People understandably worry that a missed dose has undone their treatment. The evidence gives some reassurance, but also has gaps.
Short delays are common
In everyday practice and in research studies, many people had some doses postponed and still completed treatment.
Long gaps are less studied
There is little research on what happens with gaps of many weeks, which is why rebooking quickly is advised.
One missed dose is not a failure
What matters most is getting back on schedule and completing the planned course where it is safe to do so.
What this page cannot tell you
It cannot tell you whether your particular delay will affect your outcome. Your oncologist knows your cancer and can explain that.
Early breast cancer
Missed doses during the fourteen-cycle course
After surgery, T-DM1 is usually given for fourteen cycles to people whose cancer was not fully cleared by chemotherapy before the operation. The aim is to lower the chance of the cancer coming back.
Completing the course
A missed dose is normally rebooked rather than skipped, so the total number of cycles stays the same. The course simply finishes a little later.
If side effects cause repeated delays
Some people have several delays because of low platelets or liver changes. Your team may lower the dose, and occasionally they may switch you back to trastuzumab to finish the year of HER2 treatment.
Radiotherapy and hormone tablets
If you are also having radiotherapy or taking hormone tablets, keep going with those unless your team advises otherwise. A missed T-DM1 appointment does not usually change them.
Advanced breast cancer
Missed doses when treatment is ongoing
In advanced cancer, T-DM1 is usually given for as long as it keeps the cancer controlled. The goal is to keep treatment regular while living as fully as possible.
Planned breaks
Sometimes a short break is planned for a family event, travel or recovery from side effects. Discuss this in advance so the timing is safe.
Unplanned gaps
If an appointment is missed, contact the unit and rebook. Your team may review your symptoms and decide whether a scan is needed sooner.
Telling your team what you feel
If missed appointments happen because treatment feels too hard, say so. Side effects can often be eased, and your preferences shape the plan.
Commonly believed
What people assume about missed doses
A missed dose means starting the whole course again.
The missed dose is rebooked and the course continues; there is no restart.
The next dose will be doubled to catch up.
Doses are not doubled. The schedule moves forward from the date of the delayed dose.
A delay chosen by the team means the treatment has failed.
Delays for low platelets or liver changes are routine safety steps.
It is better to wait for the next planned date.
Guidance is to give the missed dose as soon as possible, not to wait.
Questions we are asked
Common questions about missed T-DM1 doses
How late can a dose be before it matters?
There is no exact cut-off. A delay of a few days is common and unlikely to make a meaningful difference. Longer gaps are less studied, so the advice is to rebook as soon as possible. Your oncologist can tell you whether a longer delay in your case needs any extra steps.
Will I get a bigger dose next time?
No. The dose is based on your weight and on how you coped with earlier doses. It is not increased to make up for a gap. If your weight has changed noticeably, the dose may be recalculated, which is a routine step and not related to the delay itself.
Will the drip take longer after a delay?
Usually not. If you managed earlier doses well, the rescheduled dose is normally given at the same speed as your last one. Your team will still watch you during and after the infusion, as they would at any visit.
I missed a dose because I felt unwell. What now?
Tell your team what symptoms you had. Fever, bleeding, yellowing of the skin or eyes, breathlessness or a new cough need prompt review. They may run tests and wait until you recover before giving the dose safely.
Does a missed dose change my heart scan schedule?
Heart scans are usually repeated every few months during HER2 treatment. A short delay rarely changes that plan, but ask your team to confirm when your next scan is due so it still happens before the dose that needs it.
Can I plan a break for a wedding or travel?
Often a short adjustment is possible if you discuss it well in advance. Your team can suggest the safest timing, such as moving a cycle by a few days. Avoid simply not attending, because unplanned gaps are harder to manage.
Does a delay affect contraception advice?
No. You still need reliable contraception throughout treatment and for seven months after your last dose, because T-DM1 can harm an unborn baby. If the course finishes later because of delays, that seven-month period starts from the later final dose.
What if delays keep happening because of side effects?
Your team may lower the dose, which often allows treatment to continue more smoothly. If problems persist, they may discuss switching to another HER2 treatment. These decisions are common and are made to keep treatment both safe and effective for you.
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Speak to a breast cancer specialist
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Sources
- European Medicines Agency — Kadcyla: product information
- Cancer Research UK — Trastuzumab emtansine (Kadcyla)
- Macmillan Cancer Support — Trastuzumab emtansine (Kadcyla)
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.