Bathroom lighting is a mirror problem before it is a room problem

What follows is the working version of bathroom lighting: the decisions in the order you actually meet them, with the reasoning attached.

Why overhead mirror lighting is unflattering

A source directly above the face throws shadows into the eye sockets, under the nose and under the chin, which reads as tired and older. This is the standard bathroom arrangement, and it is why so many people describe their bathroom mirror as unforgiving. It also puts the light behind your head when you lean towards the mirror, so the closer you get, the less light reaches your face.

The problem is geometry, not quality, and no amount of extra brightness corrects it.

Light from the sides is the fix

Two sources at roughly face height, one on each side of the mirror, cross-light the face and cancel each other's shadows. Wall lights, vertical strips, or a mirror with side illumination all achieve this, and the effect is immediately obvious.

Live with it a while and where side space is tight, an illuminated mirror with a diffused perimeter or a backlit edge does an acceptable approximation. Adding a light above as well is fine once the sides are there, because it is no longer doing the work alone.

Colour rendering matters more here than anywhere

A bathroom mirror is where people assess skin, shave and apply makeup, all of which depend on accurate colour. A low-CRI source makes skin look grey and makes makeup applied in the bathroom look wrong in daylight. A CRI above ninety, at around three thousand kelvin, is a good general specification for a domestic bathroom.

Cooler light is crisper for detail and starts to look clinical, which is a personal trade rather than a rule.

Zones and IP ratings are a safety requirement

Bathrooms are divided into zones by proximity to water, and each zone requires fittings with a minimum ingress protection rating. The exact zone definitions and required ratings are set by national wiring regulations and differ between countries. Getting this wrong is not a cosmetic matter; it is an electrocution risk in a room where people are wet and often barefoot.

Bathroom electrical work is notifiable or restricted in many jurisdictions and should be carried out by a qualified electrician.

The room needs a second setting

A bathroom used for a bath in the evening needs a low warm light, and the same room used for getting ready at seven in the morning needs a much brighter one. A single bright ceiling light gives one of those and makes the other impossible. A dimmable circuit, or simply a second low-level fitting on its own switch, covers both for very little cost.

The quieter point is that low-level or plinth lighting is also the practical answer for using a bathroom at night without fully waking up.

Reflection is an asset here

A bathroom is full of hard reflective surfaces, so light bounces efficiently and a bathroom generally needs less output than people install. Aiming light at a wall or the ceiling rather than straight down produces a softer, more even result in a small tiled room. Mirrors placed to reflect a window bring real daylight deeper into what is often a poorly lit room.

Underneath it, a grid of downlights in a small bathroom is almost always more fittings than the room needs and the least flattering arrangement available.

The takeaway

Put light on both sides of the mirror at face height, specify high CRI, and give the room a low setting as well.

The best rooms look like a decision, not a purchase.