How long for drowsiness and dizziness and sleep issues to pass on Lamictal (25 mg)?

Hi, Ekamisakis!
Most side effects generally resolve over a period of 7 to 10 days, occasionally a few days longer. 25mg is the low initial dosage and after 2 weeks, depending on your response, it may be increased. Because it's a low dose maybe it won't take much longer for your metabolism to adjust.
As far as weight gain and libido it's about a 50/50 chance with a slight advantage to the libido.
"Metabolic
Common (1% to 10% of users): Weight decrease, weight gain.
Genitourinary
Common (1% to 10% of users): libido increase.
Uncommon (0.1% to 1% of users): Libido decreased"
Lastly, this is a link to users reviews:
https://www.drugs.com/comments/lamotrigine/lamictal.html
Hope this is helpful.