As a general guide, if you are taking finasteride for male patterned hair loss (which I assume you are), you are looking at a minimal dosing of 3mg per week. Side effects, by definition, are dose dependent and slowly increasing the dose and monitoring yourself closely for such side effects allows one to immediately stop the medication if you encounter any.
Additionally, finasteride has a better treatment effect in combination with minoxidil and you should consider using both synergistically.
Finasteride is also used for female patterned hair loss and can be dosed at 2.5 – 5mg per DAY.
You can read this article for more information about hair loss treatment in Singapore.