I am developing side effects from minoxidil

I use 3 pr 4 ml daily of minoxidil and I am scared of developing cardiovascular sides. I am young and it has been 3 years that i have been taking it.

Does low dose oral min ( 1.5 mg ) is safer?

Like all drugs, there can be side effects and one of the many side effects can be dangerous to the heart. If you take minoxidil, as any drug, and you get side effect, speak with your prescribing doctor or if it is not a life altering drug like minoxidil, just stop it. Are you taking it orally now?  If so, what dose are you taking?  Generally, the 1.5mg oral dose is safe, but there are exceptions and that is why you need to see your doctor.