Note: These are only a few problems that rabbits have. If you have any serious concerns regarding your pet's health please consult with a vet immediately!
Rabbits by nature are animals who are always on the defense. They can never show that they are sick, in pain, or injured for fear that a predator would take advantage of their disability and kill them. So, how are you, the bunny parent, able to tell if your pet is ill? It is not easy but that is why you must pay attention to your rabbit's behavior, eating habits, and hygiene.
For starters, I want to suggest that you take a look online or in a phone book to see if there is a local 24 hour emergency animal hospital nearby. While you're at it, check to see if there are vets around you that specialize in rabbits. Many places will say that they have an "exotics" pet doctor, which supposedly includes rabbits in their field of expertise. I personally feel that you should find a place that actually has a rabbit doctor though. It's nice and settling to know that someone has thorough knowledge of your bunny's body and health. Once you find a doctor, schedule an appointment and bring your bun in for a check up, even if you don't think your rabbit is sick. Building a relationship between your rabbit and it's doctor is helpful because your doctor's office will file any info about your bunny. This includes, any health problems, spay/neuter appointments, previous medicines the rabbit took, teeth and nail clipping appointments etc. If there is ever an emergency, call ahead before taking your bunny to the office to make sure your doctor or another "small animals" doctor is present.
• Okay, so let's talk about your bunny's behavior. I've heard a few pet owner's tell me that their bunny acts "weird" sometimes. They'll tell me that their bunny isn't eating, they are pooping different looking poops, chewing everything, etc. My answer to them is usually this response, if your rabbit is acting weird then its one of a few things; it's either bored, sick, annoyed, or just being goofy. I'm going to help you differentiate your bunny's behavior and make sure you're not ignoring your pet's needs for medical treatment or playtime.
• When your rabbit isn't eating or drinking, chances are that its gi-tract/digestive system is slowing down. Sometimes if you put your ear to your bunny's belly you can hear stomach sounds. If you don't hear much movement, then your bun is in trouble. It's very important to make sure that your rabbit's teeth are not mis-aligned. Poor teeth alignment make it hard for your rabbit to chew and swallow its food. Bring your rabbit to the vet immediately. If you aren't able to do this right away, make sure your bunny continues to get water. Get a little syringe and fill it up with water. Push your bunny's cheeks back and squeeze the syringe into your bun's mouth. A little water goes a long way with keeping your bunny alive. If you don't know how to snip your rabbit's teeth, then don't! You could risk splitting them and causing more damage. Do stay by your rabbit's side until you can get an appointment. I would also recommend you visiting this pet education site to better understand and to see illustrations of healthy and poor rabbit teeth.
• Changing your rabbit's diet can cause weird poops, but that doesn't necessarily mean your rabbit is sick. If your rabbit has runny poop or diarrhea then your bunny is sick, and needs to see a doctor. Same thing goes for really smelly thick urine, your bun could have a kidney problem, so get your bun to the doc if your rabbit's health isn't improving.
• If your bunny is chewing everything, then it is either trying to file down its teeth so it can eat, or tell you that you need to play with him/her.
• Rabbits are always seen scratching and grooming themselves but if your bun's head is tilted and it keeps scratching its ear, then it might have a problem. Check your bunny's ear for ear mites. I recommend taking your bun to the doctor if you see mites and feel uncomfortable squirting in some ear drops.
• Check your bun's bottom for "litter rot." If you have an over weight or old bunny then you need to make sure it's bottom is clean or groomed. Litter rot can happen when a rabbit can't reach its behind to groom itself. If you do find some litter rot, I recommend you carefully cutting off some of your bun's hair, and again if you are uncomfortable bring your bunny in to the doctor for a trim.
• Fly strikes are important to watch out for as well. Flies lay their eggs in rabbit feces and then the baby larvae use your bunny as a living host. So be sure to clean your bunny's cage often to avoid fly strikes!