How to use the Pet Heartworm Prevention Dose Checklist
Skipping a single month of heartworm prevention leaves a window in which infection can take hold, so a record of which months were missed matters. Check off the months of the year when a dose was actually given and this checklist lists the gaps, then adds one month to the most recent dose date to show the next due date and the days left or overdue.
The schedule follows the CAPC recommendation of one dose per month, year round. Prevention is advised without a seasonal break even in colder regions, so all twelve months are counted here. The next due date is the most recent dose date plus one month, clamped to the final day of the month when that calendar day does not exist (as of October 2026).
Heartworm preventives are prescription products, and after a long gap a test may be required before restarting. Product names and doses are not covered here, and broader internal or external parasite schedules are outside the scope of this tool. This tool is for reference only and does not replace veterinary care. Contact your veterinarian right away if you notice symptoms or suspect a problem.
Frequently Asked Questions
CAPC recommends a dose once a month, year round, regardless of local temperature. This checklist uses all twelve months, so a blank winter month is listed as missed.
This tool does not make that call. After a long gap a heartworm test may be needed before restarting, so discuss the restart and any testing with your veterinarian.
One month is added to the most recent dose date. When that calendar day does not exist, the final day of the month is used, and the days left or overdue are shown.