The English phrase 'what's up?' translates directly into Hindi as क्या चल रहा है? Or 'kyā hō rahā hai?' If you were asking someone about their health in a more formal setting, you might prefer to ask 'How is your health?', which in Hindi becomes क्या हाल है? Or 'kyā hāl hai?'
Remember that colloquial phrases in English like 'what's up?' may not carry the same mean in another language, even when translated, so if in doubt, keep with the formal greeting. You may also find, with Hindi in particular, even polite phrases may change dependent on who you are talking to (a stranger, or an elder, as opposed to a friend) and tone of voice can be as important as what you say.
Basic Health Questions in Hindi
Hello, how are you? - नमस्कार क्या हालचाल हैं? Or Hailō, āpa kaisē haiṁ?
Are you well today? - तुम अच्छी तरह से आज कर रहे हैं? Or Āpa acchī taraha sē āja kara rahē haiṁ?
Do you need a doctor? - तुम एक डॉक्टर की ज़रूरत है? Or Āpa ēka ḍŏkṭara kī jarūrata hai?
I am well, thank you. And you? मैं अच्छी तरह, धन्यवाद हूँ। और आप? Or Maiṁ acchī taraha sē kara rahā hūm̐ , dhan'yavāda. Aura āpa?
450,000,000 people around the world speak Hindi and if you're planning to visit them, they'd love to hear you make the effort of speaking a few basic Hindi phrases. Here's a good place to start: