Multivitamin
Also called: multivitamins, A to Z tablets.
Last reviewed 2026-09-16. How this works.
General use Grade C
Human evidence exists and does not settle it.
A standard multivitamin was not linked to worse outcomes during chemotherapy, and not to better ones.
No harm signal in the chemotherapy study, and no benefit either.
The claim
The claim, made in both directions, is either that a multivitamin supports the body through treatment or that it interferes with it. This entry is mostly here to answer a question people are anxious about.
What it does
A multivitamin is a mixture at ordinary intakes rather than a single compound at a high one, which is why it behaves differently from the individual vitamin entries in this chapter.
The evidence
The most useful study followed people taking supplements during chemotherapy inside a cooperative group trial. Multivitamin use was not associated with poorer outcomes.1
That is a reassuring absence rather than a benefit. Nothing in this record shows a multivitamin improves any cancer outcome.1
One limit matters. Supplement use was not randomised within that trial; people chose what they took. So this is observation inside a trial rather than a trial of supplements, and the same study found a signal in the other direction for one specific vitamin, which has its own entry here.1
The studies this rests on
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Supplement use during chemotherapy within SWOG S02211
An observational study, measured survival.
multivitamin use not associated with poorer disease-free or overall survival.
What is absent
No trial has randomly assigned people to take a multivitamin during cancer treatment or not. The evidence here is what people chose to take, observed inside a trial of something else.
Scope: multivitamin use during cancer treatment.
Established by trial scope, checked 2026-09-16. Result: supplement use in the only study in this record was self-selected rather than randomised.1
What to ask
Is there anything I take that you would rather I stopped while I am on this treatment?
The dish-to-person gap
A multivitamin is a mixture rather than one compound, so no single pharmacokinetic profile applies to it.
When to call your team — no warning signs are recorded
Whatever you are taking or thinking of taking, the people treating you can only weigh it if they know about it. That is true when nothing has been written down here, and it is most true then.
The register records no warning signs for a multivitamin. That is not a statement that nothing can go wrong.
Interactions
The register holds no measured interaction between a multivitamin and a cancer treatment class. Chapter 16 of the book covers supplement interactions in general, and an empty list here means nobody has measured this one.
Nobody having looked is not the same as nothing being there. That is what this line says and all it says.
The whole interaction list, and how to turn it into a pharmacy review request.
Find a trial instead
This is a general supplement rather than an intervention with recruiting cancer trials attached.
References
Ambrosone CB, Zirpoli GR, Hutson AD, et al. Dietary supplement use during chemotherapy and survival outcomes of patients with breast cancer enrolled in a cooperative group clinical trial (SWOG S0221). Journal of Clinical Oncology 2020;38(8):804-814.
How this was reached: transcribed from chapter note, via docs/CHAPTER-NOTES.json, chapter 17 note 12. The author string is abbreviated in the source that was read and has not been expanded.