I've always heard that not taking enough glucosamine will have no benefits. With that in mind, I use a liquid form of glucosamine HCl and follow the instructions on the bottle. My dog is 10 and was walking a bit "stiffly". The vet diagnosed arthritis. He recommended glucosamine and I started with pills, but what a nightmare..she knew what I was doing, even crushing in food. I switched to the liquid form and she actually LIKES it. Go figure. Anyway, after about 5 months, I have seen a considerable improvement. Sassy moves better. I follow the recommended dosages on the bottle and that seems to be doing the job.
So, in reply to your question, you should follow what the label says....if the glucosamine is packaged for humans, you may have to calculate your dosage based on body weight, but I think that the stuff should be given daily in the correct dose, not every couple of days. I think, with the pills, it was 30-40kg you use 1,000mg/day (500mg AM and 500mg PM), but that was a pet formulation of glucosamine. You may want to check with your vet, if unsure.
