Yeah its always just mg/kg
A calculator always helps, or having a scale that reads in kg like the one I have from Reptile Basics
You CAN always just remember that a kg is 1000 grams, so 3400 grams is 3.4kg, or like 950 grams is .95kg and so on....
You of course would always want to have a Fecal/Culture done to be sure you actually need ANY medication.
Of the liquids I had to use to be given orally, its always been the consistency of about milk if that helps.
Like I said the math is really easy, say you have a 1200 gram animal and the dosage for the drug is 75mg/kg
Just convert your 1200g to kg=1.2 kg
75 mg/kg times 1.2=90 mg
So you would just need to find out the concentration of the drug and dispense accordingly, something your Vet could always do for you and you could rest assured its correct.