Phuket is a heavily visited, tourism-dependent island with decent healthcare infrastructure, but a few practical precautions are worth planning around.
Travel insurance
Comprehensive travel insurance that covers medical treatment and evacuation is strongly recommended — private hospital treatment in Thailand is good but not free, and costs are billed directly to patients without insurance.
Hospitals
Phuket has several private hospitals with international patient departments used to treating tourists, generally offering faster service than public hospitals in exchange for higher cost.
Road safety
Road accidents, particularly involving rented scooters, are the most common serious safety issue for visitors. Wearing a helmet, holding a valid international driving permit, and being cautious on unfamiliar mountain roads (especially around Patong and Kamala's steep hill routes) all measurably reduce risk.
Sun and water
Strong sun year-round and rip currents on some west-coast beaches during monsoon season are worth respecting — look for posted flag warnings on patrolled beaches.