Best flea, tick and heartworm prevention for dogs

Simparica Trio is dosed by dog weight, so the right pick is the band your dog falls in — every option is the same once-monthly chew for fleas, ticks and heartworm.

• Top pick: the 11.1–22 lb six-month pack. That band covers the largest share of small and medium dogs, and six chews means no monthly reordering.
• 2.8–5.5 lb, six months: for toy and very small dogs — the band where counting pounds matters most.
• 88.1–132 lb, six months: for large and giant breeds; a three-pack version suits a shorter run or a first try.

Small and medium dogs above 22 lbs have their own band, and most listings are prescription items, so your vet's approval is needed.