Pet Medication Dosage Calculator

This calculator estimates a starting-point dose for a handful of common over-the-counter medications by scaling a per-pound rate (or, for melatonin, a weight band) to your pet's weight, and it treats dogs and cats as genuinely different animals rather than applying one rate to both — species matters enormously in veterinary dosing because dogs and cats metabolize many drugs at very different rates. For Benadryl (diphenhydramine), the calculator halves the per-pound rate for cats and caps any cat dose at 25 mg, a deliberately conservative starting point rather than a precise pharmacological cutoff — mainstream veterinary dosing bands actually put cats and dogs in a broadly similar 1-2 mg/kg range, with cats' somewhat slower drug clearance arguing more for a longer interval between doses than for a smaller dose. For aspirin, the difference for cats is not a smaller dose but a hard stop: the calculator zeroes out the dose entirely and displays an explicit warning, because cats lack the liver enzyme (glucuronyl transferase) that dogs and humans use to safely clear aspirin, and doses that are routine for dogs can accumulate to toxic levels in cats. Frequency matters as much as dose size: this tool caps the effective doses-per-day at each medication's published safe maximum — aspirin at 2/day (its roughly 12-hour dosing interval; more frequent dosing pushes toward the ~50 mg/kg/day mild-toxicity threshold), Benadryl at 3/day, and melatonin and fish oil at 2/day — and the Notes field says so whenever your entered frequency was capped, because repeated dosing above the safe interval accumulates toward toxic levels even when each individual dose looks reasonable on its own. Dog aspirin specifically should not be continued beyond about three consecutive days without veterinary follow-up.

Melatonin here uses the standard weight-banded doses from veterinary guidance (1 mg under 10 lb, 1.5 mg from 10-25 lb, 3 mg from 26-100 lb, 6 mg above 100 lb) rather than a straight per-pound rate, since real dosing charts step at weight breakpoints instead of scaling continuously. Fish oil dosing targets EPA+DHA content specifically (20 mg/lb), not total fish oil product weight, since most capsules are only a fraction EPA+DHA by weight. Daily dose multiplies the single dose by the (capped) number of times per day it's given, and weekly dose extends that across seven days — both scale directly with dosing frequency, independent of pet weight. What this tool does not account for: your pet's individual health conditions (kidney or liver disease change safe dosing substantially), drug interactions with other medications, or the fact that these are general starting-point figures, not a substitute for veterinary guidance — the description on this page and the notes field both say so, and that's not boilerplate here.