Week 8 carries the first vaccine, the 700 to 900 g weigh-in, three socialization items and a 14-day observation window that decides whether the kitten is out of the woods. Miss the window and a mild reaction becomes an emergency you find at midnight.
Why the first shot lands at week 8
Antibodies from the queen protect a kitten for the first weeks and also block vaccines. That maternal antibody fades somewhere between 6 and 12 weeks, and no test at this price tells you exactly when it dropped in one kitten. So the schedule assumes the worst: first FVRCP at 8 weeks, then repeats every 3 to 4 weeks until the kitten is 16 to 20 weeks old, for 2 to 3 shots in total.
A kitten vaccinated at 8 weeks and then not again until 20 weeks has a gap of 12 weeks, which is the common way kittens end up under-protected. The interval matters more than the brand. Rabies goes at 12 to 16 weeks, and FeLV at 9 to 12 weeks if the kitten will live with other cats or go outside.
The 700 to 900 g band
Two weeks ago the band was 400 to 600 g; at 8 weeks it is 700 to 900 g; at 12 weeks it is 1.2 to 1.6 kg. That is a gain of 100 to 150 g a week, or 15 to 20 g a day, and it fits the 100 g per week of age rule closely enough to use as a sanity check.
A kitten at 720 g is fine. A kitten that was 610 g at week 6 and is 700 g now has gained 45 g a week and needs a stool sample, a body condition score and a look at whether it is actually eating solid food. Weight is the cheapest diagnostic you own: 3 mornings, 1 g scale, same hour.
What the first visit covers
The vet weighs the kitten, listens to the chest, checks the umbilicus and the teeth, takes a temperature, and asks 3 questions about appetite, stool and energy. The injection takes 5 seconds; the exam takes 15 minutes and is the part that catches a heart murmur or an umbilical hernia before it becomes surgery.
Ask for the weight in grams on the record, not just a tick in a box. A kitten whose 8-week weight is written down can be compared at 12 weeks and 6 months, and a flattening curve shows up 4 to 6 weeks before the kitten looks thin.
| Item | Normal range | Recheck | What to do |
|---|---|---|---|
| Weight | 700-900 g | 7 days | 1 g scale, before the first meal |
| First FVRCP | Week 8 | 21-28 days | Then repeat to week 16-20, 2-3 shots total |
| Temperature | 38.1-39.2 C | 24 hours | Only if the kitten is quiet or off food |
| Meals | 4 a day | 14 days | 60-90 kcal a day, wet or soaked dry |
| Observation | 14 days | Day 14 | No new cats, no bath, no outdoor access |
The 14-day observation window
Fourteen days covers the two things that go wrong after week 8: a vaccine reaction in the first 48 hours, and an incubation period picked up before the shot. Count day 1 as the day of the injection and keep a note each morning for 14 days: weight, appetite, stool score, energy.
Inside those 14 days, no bath, no new cats, no dog park, no outdoor access, and no visitors handling the kitten for the first 48 hours. A kitten that has just met a vaccine is mounting an immune response and does not need a second stressor. If the kitten came from a shelter or a multi-cat house, the same 14 days is the quarantine before it meets a resident cat.
Normal after a shot: sleepier for 24 to 48 hours, a small lump under 1 cm at the injection site that fades in 7 to 14 days, and a mild appetite dip for 1 meal. Not normal: facial swelling, vomiting more than 2 times in 12 hours, diarrhea, a temperature over 39.5 C, or a kitten that will not stand.
Three socialization items for this week
Week 8 is still inside the sensitive period, and 3 items are enough. More than that and you cannot tell which one caused a reaction.
- Handling. 3 sessions a day, 30 to 60 seconds each: lift, hold against the chest, touch 1 paw, 1 ear, open the mouth for 2 seconds. Stop while the kitten is still leaning in.
- Sounds. Doorbell, vacuum at 3 m, dishes, at 50 to 60 dB for 30 seconds, 1 sound a day. Pair each with 1 treat within 1 second of the calm moment.
- Carrier and car. Carrier stays out with a blanket inside; door closed for 2 minutes on day 1, 5 minutes by day 7, engine on parked for 3 minutes at the end of the fortnight.
Feeding at 700 to 900 g
Four meals a day, 60 to 90 kcal, which is 90 to 130 g of wet food or 30 to 40 g of dry. By 12 weeks the count drops to 3 meals, and by 6 months to 2. Leave nothing down between meals: free-feeding a kitten this age is how a 900 g cat becomes a 5 kg cat with a body condition score of 8.
Litter, sleep and the room
Litter stays 3 to 4 cm deep, unscented, sides under 5 cm, scooped twice a day and changed fully every 7 days. Kittens sleep 18 to 20 hours a day at this age, in 4 to 6 blocks, and a kitten that sleeps 14 hours and screams at 03:00 is overtired, not naughty.
Call the vet within 24 hours for
- No gain across 2 weekly weigh-ins, or any loss
- Temperature under 37.8 C or over 39.5 C
- Vomiting 3 times in 12 hours, or refusing 2 meals
- Diarrhea lasting 24 hours, or blood in the stool
- A lump at the injection site over 2 cm, or one still there at day 21
The week-8 checklist
- Weigh 3 mornings and confirm the number sits inside 700 to 900 g.
- Book the first FVRCP and the 3 to 4 week booster date in the same call.
- Write day 1 of the 14-day window on the calendar, with a daily note line.
- Pick 3 socialization items and put them in the same order every day.
- Move to 4 measured meals and stop leaving dry food out.
- Photograph the vaccination record and keep the weight log next to it.
The three numbers that matter this week are 700 to 900 g, 1 shot, 14 days. Get the weight on paper, keep the window boring, and week 12 turns into a single weigh-in at 1.2 to 1.6 kg. For what comes before, see the week-by-week milestones; for the handling that runs alongside the shots, the socialization checklist; for a breed that suits the household, the breed quiz.
Terms mentioned in this article
Frequently asked
Is 8 weeks too early for the first vaccine?
It is the standard start. Maternal antibodies block vaccines, and they fade somewhere between 6 and 12 weeks with no cheap way to tell when in an individual kitten, so the schedule starts at 8 weeks and repeats every 3 to 4 weeks until 16 to 20 weeks. That gives 2 to 3 shots in total and covers the window where protection is uncertain.
How much weight should an 8-week kitten gain in a week?
Expect 100 to 150 g a week, or 15 to 20 g a day, which takes a kitten from the 400 to 600 g band at week 6 to 700 to 900 g at week 8 and 1.2 to 1.6 kg at week 12. Weigh 3 mornings on a 1 g scale before the first meal; two flat weeks or any loss means a stool sample and a vet visit.
What counts as a vaccine reaction I should worry about?
Sleepiness for 24 to 48 hours, a lump under 1 cm that fades in 7 to 14 days, and a mild one-meal appetite dip are normal. Facial swelling, vomiting more than 2 times in 12 hours, diarrhea, a temperature over 39.5 C, or a kitten that cannot stand are not, and need the vet the same day. Note that reactions are most likely in the first 48 hours.