Is NFC dangerous for health?
The exchange uses a weak magnetic field over a couple of centimetres, in a part of the spectrum that is non ionising, which is a different physical category from the radiation the question usually has in mind. Medical implants are a separate question with its own guidance from device manufacturers.
A different category
The word radiation carries the association of the ionising kind, which has enough energy per photon to break chemical bonds. That is a property of much shorter wavelengths.
NFC operates far below that, in a range where the mechanism is inductive coupling between two coils rather than radiation propagating away from an antenna.
The distinction between coupling and radiating is explained on the physics side of the site, and it is the reason the analogy people reach for does not apply.
Internationally, the reference is the ICNIRP guidelines for radiofrequency fields, which cover 100 kHz to 300 GHz and therefore include the 13.56 MHz NFC works at. National authorities set what applies where you are. Those bodies rather than this page are the authority on any threshold, and none is quoted here.
Weak and brief
Two features distinguish an NFC exchange from most wireless activity a phone performs.
The field is only useful across a couple of centimetres, which is why it works at all: it is not designed to reach anything further and does not.
And the exchange lasts a fraction of a second, once, when you deliberately hold two things together. It is not continuous and it is not passive.
The same phone maintains cellular and wireless network connections continuously, at greater range, all day. Anybody concerned about exposure has already accepted a great deal more than NFC contributes.
Implanted medical devices
This is a separate question and a legitimate one, and it is not answered by anything above.
Manufacturers of pacemakers, defibrillators and similar devices publish guidance on magnets and on wireless equipment, including recommended separations. That guidance is specific to the device and is the authority. The United States Food and Drug Administration has published on the magnets in phones and smart watches specifically, which is a separate question from the NFC field and the one that concerns implanted devices.
Some phones and accessories also contain magnets, which is a separate matter from NFC and is the subject of much of the manufacturer guidance.
The right action for anybody with an implanted device is to read what their own manufacturer says and to ask their clinician, rather than to generalise from a documentation site.
Where to take the question
For general exposure, the national authority responsible for it, which publishes in plain language and is the body whose numbers mean something.
For an implanted device, the manufacturer of that device and the clinical team who fitted it.
For the physics of why NFC is not the thing people picture, the explanation on this site is complete and requires no medical judgement.
This page deliberately states no threshold and gives no medical advice, because doing so from a technical site would be a false authority.
Frequently asked questions
Is NFC radiation harmful?
It operates far below the ionising range, and it couples between coils rather than radiating. Exposure thresholds are set by national authorities.
How long does the field last?
A fraction of a second, once, when you deliberately hold two things together. It is neither continuous nor passive.
Is it safe with a pacemaker?
That is a question for the device manufacturer and your clinician. They publish specific guidance, including on magnets in phones.
Why does this page not give numbers?
Because thresholds are set by health authorities, and a technical site quoting them would be a false authority.