I Feel Sick
A direct way to say 'I am sick.' Use 'enfermo' if you are male, 'enferma' if you are female.
A slightly softer way to say 'I don't feel well.' It is very common and polite.
Use this for 'I feel dizzy' or 'I feel nauseous.' Use 'mareado' for male, 'mareada' for female.
Excuse me, I feel sick. Is there a bathroom nearby?
I'm not going to work today because I'm sick.
I don't want to eat, I don't feel well.
The boat trip was long. Now I'm a little dizzy.
'Me siento mal' and 'Estoy enfermo/a' are universally understood and used.
While the main phrases are used, it's also very common to use the verb 'encontrarse'. For example, 'No me encuentro bien' (I don't feel well) is frequently heard.
You might hear 'Me siento malo/a,' which is a common colloquial variation of 'Me siento mal.'
For stomach-related sickness, the phrase 'Estoy descompuesto/a' is very common, meaning 'I have an upset stomach.'
The standard phrases 'Me siento mal' and 'Estoy enfermo/a' are the most common. No significant local variation for this basic expression.
Using 'ser' instead of 'estar' or 'sentirse'. For example: 'Soy enfermo'. — Being sick is a temporary state, not a permanent characteristic. Use 'estar' ('Estoy enfermo') for states or the reflexive verb 'sentirse' ('Me siento mal'). 'Ser' is for permanent traits like 'Soy alto' (I am tall).
Forgetting the reflexive pronoun 'me'. For example: 'Siento mal'. — The verb is 'sentirse' (to feel), which is reflexive. You need the pronoun 'me' to indicate the feeling is happening to you. 'Siento' by itself means 'I feel' something external, like 'Siento el frío' (I feel the cold).
Literally translating 'I am sick' as 'Yo soy enfermo'. — This is a combination of two mistakes. It incorrectly uses 'ser' and also has an unnatural word order for a simple statement. The correct and natural way is 'Estoy enfermo/a' or 'Me siento mal'.