When cats are sick, they may change their posture or the way they lie down to help alleviate discomfort or pain. However, the way they lay down when sick can vary depending on the type of illness and the individual cat's personality and preferences. Some cats may lay curled up in a tight ball with their paws tucked under their body, as this position can help conserve body heat and make them feel more secure. Other cats may lay stretched out on their side or stomach, with their limbs extended, which may indicate they are trying to relieve pressure on a particular area of their body. Some cats may also lay in a hunched position, with their back arched and head down, which can be a sign of discomfort or pain. When a cat is sick, they may not feel up to grooming themselves as they usually do, which can result in a scruffy or unkempt appearance. Additionally, cats may purr not only when they are happy but also when they are anxious, or in pain, so excessive purring can be a sign that something is wrong. If a cat is having trouble breathing, they may also avoid lying on their side and instead keep their head raised to help them breathe more easily.