What do you say in Spanish to inquire about a friends health?

There are various ways. you could say "¿Te encuentras bien?" , literally "Do you find yourself well?" but would probably be translated as "Are you OK?".

Another possibility is "¿Sientes bien?" or "Do you feel well?"

You could try the standard "¿Cómo estás?" or "How are you?".

"¿Qué tal con tu salud?" is "What's up with your health?"