Lamictal - Is it normal to have diarrhea and severe headaches directly after increasing to 75 mg?

Hi, Ekamisakis!
These are common side effects:
"Very common (10% or more of users): Dizziness (38%), headache (29%)
Very common (10% or more of users): Diarrhea (10%)
Common (1% to 10% or more of users): Depression, anxiety, irritability"
How long have you been taking it? Side effects generally resolve within two weeks or so and get better day by day. Yours may be quicker as you've been on the medication already.
If it's persistent or severe let your doctor know right away. You might need to stay on the 50mg a little longer or they may recommend a slower dosage increase. In the meantime, your pharmacist is a good source of how to manage side effects.
Regards and I hope you're feeling great soon!
Wildcat