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Flea, Tick & Heartworm Prevention Schedule (and How to Never Miss a Month)
Last updated: 20 August 2026
Flea, tick and heartworm preventatives only work if they're given on time, every time — and "every time" usually means every single month, for life. That's a lot of chances to forget. This guide covers how often each type of product is given, why the schedule can't slip, what to do when a month gets missed, and a reminder system that makes the whole thing automatic.
How often each type of preventative is given
Most modern preventatives bundle several parasites into one product, and most run on a monthly clock:
| Product type | Examples | Typical schedule |
|---|---|---|
| Oral chewables (combo) | NexGard Plus, Simparica Trio, Sentinel, Trifexis | Once a month |
| Topical spot-ons | Revolution / Revolution Plus, Advantage Multi | Once a month |
| Longer-acting orals/topicals | Bravecto (fleas/ticks) | Every 2–3 months, per label |
| Heartworm injection (dogs) | ProHeart 6 / ProHeart 12 | Every 6 or 12 months at the vet |
The "same day each month" habit matters more than which day you pick. If your pet is on two products with different intervals — say a monthly heartworm preventative plus a 3-monthly flea/tick chew — treat them as two separate schedules with two separate reminders, because they will drift apart.
Why vets say year-round, not "flea season"
The American Heartworm Society recommends year-round heartworm prevention for dogs and cats, without skipping a single month. The reasons are practical, not upselling:
- Fleas don't do winter break. They overwinter happily inside a heated home; one missed month can seed an infestation that takes months to clear.
- Ticks are active on any mild day, and some can transmit disease within 24–48 hours of attaching.
- Heartworm has no forgiving window. Preventatives work retroactively — each dose clears larvae picked up in the previous month. Skip a dose and that month's larvae get to keep developing.
- For cats, prevention is the whole game: there's no approved treatment for feline heartworm disease.
Missed a month? Do this
- Give the dose as soon as you notice — late is better than skipped for almost every product.
- Write down the actual date you gave it, and restart the monthly count from your regular day.
- If the gap was more than ~2 weeks, call your vet. For heartworm preventatives they may advise testing now and again in about 6 months, because an infection picked up during the gap won't show on a test immediately.
- Don't double-dose to "catch up" unless your vet explicitly says to.
If you genuinely can't remember whether you gave this month's dose, that's not a character flaw — it's what happens when a monthly task has no record. It's also exactly the problem a dose log solves.
A reminder system that makes missing impossible
- One "pet meds day" per month. Pick a date you already notice (the 1st, payday) and anchor every monthly preventative to it.
- A reminder that names the pet and the product. "Give meds" fails in multi-pet homes; "Milo — NexGard Plus" doesn't.
- Log it when you give it. A tap after each dose builds the history that answers "did I already give it?" and shows gaps before your vet finds them.
- Track supply too. A 6-dose box runs out in 6 months — set a refill reminder a month before the last dose so reordering never causes the gap.
PET-A was built for exactly this loop: set a monthly schedule per pet, get the reminder, tap to log the dose, and see the full history — private and on your phone.
Never miss a month again
PET-A reminds you which pet gets which preventative, logs every dose, and keeps the history vet-ready. Free for one pet.
Frequently asked questions
How often should I give flea, tick and heartworm prevention?
Most combination chewables and spot-ons are monthly, on the same day each month, year-round. Some products last 2–3 months, and vet-administered heartworm injections last 6–12 months — always follow the label and your vet.
Is year-round prevention really necessary?
Yes — the American Heartworm Society recommends it for dogs and cats. Fleas survive indoors in winter, ticks stay active on mild days, and one missed month is enough for heartworm larvae to start developing.
What if I missed a dose?
Give it as soon as you remember, note the date, and resume the normal schedule. If the gap exceeded a couple of weeks, call your vet — they may recommend heartworm testing now and in ~6 months.
Do indoor cats need prevention?
Most vets say yes: fleas hitchhike indoors and mosquitoes (which spread heartworm) get inside easily. With no approved feline heartworm treatment, prevention is the only protection.
What's the best way to remember the monthly dose?
One fixed "pet meds day" per month, a reminder that names the pet and product, and a logged record of each dose given — so doubt and drift can't creep in.