I wouldn’t think it will harm him.

What are the ingredients?

It might have sucrose or sorbitol but they are common in medications given to rabbits.

Vitamin C is not toxic to rabbits, they do in fact need vitamin C. It doesnt need to be added to their food, because their bodies are capable of synthesizing it from other molecules. This is the case with most mammals except humans and guinea pigs. Guinea pig pellets always have vitamin C added, that’s the difference between rabbit pellets and guinea pig pellets. Extreme overdoses of vitamin C could cause harm, but I doubt half a pill at one instance is considered an extreme overdose.

It could perhaps cause some stomach upset, because vitamin C is an acid (ascorbic acid). As Jerseygirl mentions, there are also other ingredients in the pills besides the ascorbic acid.

Encourage hay eating and water (a good way to increase water intake is by serving greens freshly rinsed and wet).

Sounds good! We’d be happy for updates 🙂