The Cat Coat Cycle: 3 Phases and 2 Molts a Year

Every hair on a cat sits in a follicle that runs its own 3-phase cycle, the coat as a whole is replaced in 2 molts a year, and the timing is set by 2 light signals rather than by the date. Name the phase and most shedding questions answer themselves: the fur on the sofa in April is exogen running through a few thousand follicles at once, not a deficiency.

The 3 phases of a follicle

Anagen is growth. The follicle pushes a new hair out of the bulb, and the old club hair is still anchored beside it. In the cat's undercoat anagen runs roughly 3-8 weeks; a guard hair, which is longer and thicker, can stay in anagen 12-16 weeks. Growth rate is slow by mammal standards, about 0.2-0.3 mm a day, which is why a shaved patch takes months to look normal again.

Catagen is regression, 1-2 weeks. The follicle stops producing pigment and keratin, the bulb moves upward, and the hair base hardens into a club. Telogen is rest, 4-12 weeks, with the club hair held loosely in the follicle. Exogen is the release: the club hair drops out and anagen restarts in the same pore. Exogen is short, often 1-3 weeks per follicle, and it is the only phase an owner ever sees.

Why a cat never goes bald in one go

Follicles cycle in a mosaic. Neighbours 1-2 mm apart can be in opposite phases, so hair loss is spread across the body and never leaves a bare patch the way a single-coat moult would. This is also why coats look patchy in a heavy shed rather than uniformly thin.

The pattern has a gradient. The back and flanks carry the densest, longest coat, the belly the thinnest, often 1.5-2 times shallower in coat depth. Grooming follows the same gradient, which is why the belly and the inside of the thighs mat first in a longhaired cat and why a mat there is a welfare problem, not a cosmetic one. Density itself varies widely between cats, and a shorthair with a sparse summer coat is normal variation, not a symptom.

2 molts a year, and when they run

North of the equator the spring molt runs from roughly March to May and takes 4-8 weeks; the autumn molt runs September to November and is usually shorter, 3-6 weeks. South of the equator the 2 windows flip to September-November and March-May. The spring event drops undercoat and leaves a thinner summer coat; the autumn event builds insulation back and is the one that produces the denser coat owners complain about in December.

Kittens do not follow the adult pattern. The first real molt arrives at 4-6 months, when the soft kitten coat is replaced, and the first full seasonal cycle usually settles by 12-18 months. A 5-month-old losing coat in clumps is on schedule.

Light cue 1: hours of light

The switch is tracked through day length, and the practical threshold sits near 12 hours of light per day. Above it the body reads late spring and holds a thinner coat in growth; below it, the autumn molt is triggered. An indoor cat in a room lit from 17:00 to 23:00 sees 6-8 extra hours of light a day, which pushes total exposure past 14-16 hours in winter and flattens the cycle into a year-round trickle of hair instead of 2 clear events.

A window helps more than a lamp. Daylight through glass on a bright day is 1,000-10,000 lux at the sill, while a living-room lamp gives 100-300 lux at 2 m. A cat that sits at a bright window still reads the real photoperiod even if the room lights stay on.

Light cue 2: the direction of change

The second cue is not the absolute day length but whether days are getting longer or shorter. Lengthening days drive the spring molt; shortening days drive the autumn one. This is why a cat rehomed in October may skip that year's autumn molt entirely, and why a cat flown across the equator can molt twice within 4-6 months while its rhythm re-sets.

The signal is carried by melatonin, which the pineal gland secretes through the dark hours. Long nights mean a long melatonin signal, short nights a brief one, and the follicle cycle follows that rhythm. Because melatonin tracks darkness rather than clock time, a cat kept in a constantly lit room has a blunted signal and a blunted molt.

Reference intervals for a normal coat

Phase	Duration, low	Duration, high	Follicle state	What the owner sees
Anagen	3 weeks	16 weeks	New hair forming, old hair anchored	Nothing
Catagen	1 week	2 weeks	Growth stops, bulb rises	Nothing
Telogen	4 weeks	12 weeks	Club hair held loosely	Nothing
Exogen	1 week	3 weeks	Club hair released	Hair on brush, floor, clothes

Two home measures are worth keeping. Coat depth on the back is 2-3 cm in a shorthair and 8-15 cm in a longhair, measured by parting the coat to the skin at 3 points. Shed rate can be counted by brushing for 5 minutes over a black cloth: in midwinter a few dozen hairs is unremarkable, and in a spring molt several hundred is the same normal event at a different phase. Counts vary by cat and brush pressure, so treat the number as a trend line.

When the calendar is not the explanation

5 findings move shedding out of the normal range: a bare patch that has not regrown after 8-12 weeks; symmetrical thinning on both flanks with intact skin; scale, crust or greasy sebum; scratching or over-grooming that outlasts the molt; and coat change paired with weight or appetite change. One of those is worth a note to the vet, 2 together is worth a visit.

Parasites (fleas, Cheyletiella), thyroid disease, food that is short on protein or omega-3 fats, and chronic stress all change the coat before they change behavior. A cat on a diet below about 26-30% protein on a dry-matter basis can hold a dull coat with delayed regrowth, and the fix is the bowl, not a supplement.

Working with the cycle

Brush 5-10 minutes a day from March and September, when exogen is heaviest; twice a week the rest of the year.
Keep a fixed dark period of 8-10 hours to give the melatonin signal an edge.
Log coat depth at 3 points monthly so a real change shows up against a baseline.
Do not shave for shedding; regrowth to normal coat takes 8-12 weeks and sunburn risk rises on pink skin.

If you want the digestive side of the same animal, the liver's recycling loop is covered in the bile acid cycle, and the question of how much of this coat the cat can actually see is in feline color vision.

Terms mentioned in this article

Frequently asked

My cat sheds all year, not twice a year. Is that abnormal?

Usually it is a light problem, not a health problem. An indoor cat under 14-16 hours of combined daylight and lamp light loses the sharp photoperiod switch, so follicles drift into a low-level year-round trickle instead of 2 molts. Try a fixed 8-10 hour dark room and compare brush counts over 6-8 weeks. If coat depth is also falling at 2 of the 3 points you track, or the skin looks crusty, that moves from light to vet.

How long until a shaved patch grows back?

Plan on 8-12 weeks for the skin to be covered again and 3-6 months for the coat to reach normal depth and texture. Hair grows about 0.2-0.3 mm a day, and after clipping many follicles sit in telogen for 4-12 weeks before anagen restarts, so the first 1-2 months look stalled. Guard hairs, at 12-16 weeks of anagen, come in last, which is why a regrown patch can feel softer for a while.

Does brushing reduce shedding?

It removes hair that exogen has already released, so less lands on the sofa, and it spreads sebum and prevents mats in longhaired cats. It does not change the cycle. The useful schedule is 5-10 minutes a day from March and September, when exogen is heaviest, and 2 sessions a week the rest of the year. A rubber curry comb on shorthairs and a steel comb on longhairs reach the undercoat where the loose hair actually sits.