How much hair loss is normal?

It is the first thing almost everyone searches, and the answer they find, fifty to a hundred hairs a day, has a reassuring precision to it. It is also, in practice, close to useless.

Here is why. That figure comes from studies of scalp hair cycling in groups of people, and it describes an average. Your own number depends on how much hair you have to begin with, how long it is, how often you wash it, how much you handle it, and how carefully you are looking. Someone with dense hair to their waist and someone with fine hair to their chin can shed wildly different amounts and both be entirely unremarkable.

And nobody counts. People say they count, and a few genuinely try, but hair collects in drains and on clothing and on the floor, and the hairs you can see are never all of them. A count that misses a third of the evidence is not a measurement.

The question that is actually useful

Not how much, but has it changed, and is anything else changing with it?

Shedding is a rate. What matters is whether that rate has increased relative to your own normal, whether it has stayed increased for more than a few weeks, and, most importantly, whether the amount of hair on your head is going down as a result.

Those last two things are not the same, and confusing them causes a great deal of unnecessary alarm and, occasionally, a great deal of unnecessary calm.

Shedding with stable density

You are losing more than you used to, but your parting looks the same, your ponytail feels the same, and photographs from a year ago look much like now. This often means the cycle has been disturbed and is correcting itself: the pattern seen after illness, childbirth, a period of under-eating, or a change in medication. Hair is being lost and replaced. It is unpleasant to watch and usually finite.

Shedding with falling density

You are losing more, and there is visibly less: the parting has widened, the ponytail is thinner to hold, scalp shows in light where it didn't. This means loss is outpacing replacement, or that what is being replaced is finer than what was lost. It is the combination that warrants investigation, and it is worth being seen properly.

Thinning without much shedding

The most commonly missed presentation. Hair gets progressively finer over years without any dramatic shedding at any point. People often say, with some frustration, that their hair 'doesn't fall out', and use that as evidence that nothing is wrong, when the change in calibre is the whole story.

Three things worth doing instead of counting

1. Measure the circumference of your ponytail with a piece of string, once a month, in the same place. It is crude and it works, because it measures the thing you actually care about.
2. Photograph your parting in the same light, from the same angle, on the same day of your wash cycle, once a month. Daylight, no flash, hair dry. Most people's sense of whether things are getting worse is heavily influenced by mood and lighting; a photograph isn't.
3. Look at the ends of what you're losing. A shed hair has a small pale bulb at one end. A broken hair does not. It is snapped, often short, and it means something completely different.

When it is worth getting help

• Increased shedding that has continued for more than three months.
• Any visible reduction in density.
• Loss in patches, or any change to the skin of the scalp.
• Shedding alongside fatigue, weight change, temperature intolerance or changes to your periods, worth blood work with your GP.
• Any of it worrying you enough that you are reading this at two in the morning. That is a legitimate reason on its own.