Verbseoul.
하다 verb (adj)
건강하다geonganghadato be healthy

To say to be healthy politely in the present tense, use 건강해요 (guhn-gahng-hae-yoh). Below is the full conjugation of 건강하다 across the three tenses and three everyday speech levels.

Conjugation table

TenseCasual (반말)Polite (요)Formal (합니다)
Present
건강해
guhn-gahng-hae
건강해요
guhn-gahng-hae-yoh
건강합니다
guhn-gahng-hahm-nee-dah
Past
건강했어
guhn-gahng-hae-ssuh
건강했어요
guhn-gahng-hae-ssuh-yoh
건강했습니다
guhn-gahng-hae-sseum-nee-dah
Future
건강할 거야
guhn-gahng-hahl- -guh-yah
건강할 거예요
guhn-gahng-hahl- -guh-yae-yoh
건강할 겁니다
guhn-gahng-hahl- -guhm-nee-dah

Other useful forms

Command Polite (세요)
건강하세요
guhn-gahng-hah-sae-yoh
Suggestion / Let's Polite (요)
건강해요
guhn-gahng-hae-yoh
Question Polite (요)
건강해요?
guhn-gahng-hae-yoh-?
Connective “and” — (고)
건강하고
guhn-gahng-hah-goh
Conditional “if” — (면)
건강하면
guhn-gahng-hah-myuhn
Noun form — (기)
건강함
guhn-gahng-hahm