Cómo decir que te encuentras mal (coloquial de España)
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In Spain, the most colloquial way is: "estar malo." E.g.: "Estoy malo" / "Me he puesto malo" (in informal speech, instead of "estoy enfermo").

"pachucho" / "pocho" = feeling a bit unwell, mildly sick, said in an affectionate way. E.g.: "Estoy un poco pachucho hoy." (Rough idea: nothing serious, just feeling weak/off.)

Careful with "constipado": in Spain it means "to have a cold, a runny nose." It is NOT "constipated" in English. E.g.: "Estoy constipado, tengo mocos."
"estar hecho polvo" = to be very weak/exhausted because of illness. E.g.: "Con la gripe estoy hecho polvo." (In English: "I feel completely wiped out.")

At the pharmacy/doctor’s office: "tengo mocos" (I have a runny nose), "tos seca" (dry cough), "¿andas con décimas?" ("décimas" = a slight fever, a bit over normal temperature). These are very common phrases in Spain.
