Spironolactone Dosage Change?

You're correct in understanding that Spironolactone often requires 2-3 months before significant improvements in acne are noticed. This is due to the time needed for the medication to exert its effect on the hormonal balance which influences acne.
When the dosage of Spironolactone is increased, like in your case from 25mg to 100mg, the time frame to see an improvement may be similar to when you first started the medication. However, it can also potentially be a bit shorter since the medication has already been in your system.
While we typically say 2-3 months, it's important to remember that everyone's body responds differently to medication, and some people may see improvements sooner or later than this average time frame.
If after a reasonable period of time, you do not see the expected improvement, or if you experience any side effects, it would be important to consult with your healthcare provider to reassess your treatment plan.