Overdosing can mean too much in one go, and/or dosing again too soon.
Each of the meds will say on the bottle somewhere something along the lines of, 'repeat every x to y weeks' and/or 'do not repeat dose within xx days', so be guided by those. Generally you would never repeat a dose within the withdrawal period, either.
Also, if you are repeat dosing for one specific parasite, try not to re-dose for other parasites which are not causing a problem. So repeat doses for fluke should be plain flukicide, not a broad spectrum worm-and-fluke drench.
And don't worry, Joanne, this
is hard to get your head around; you are not alone in that! Plus, veterinary advice on best practise changes from time to time... it's no wonder we all keep asking about this each year.
One thing that will help you with planning your rotation, and knowing which stages of which parasites you are hitting, is the EBLEX Better Returns Programme Parasite Control Guide, which you can download from
hereIt's best to always go and download it, as it changes from time to time.
Shout again if you have any further questions. If I can't answer them, I know a couple of other TASers I can call on