Can a dosage increase on sertraline cause side effects such as headache and dizziness?

Thank for responding Do the side effects usually last long with dosage increases

They generally resolve in about a week or so... maybe even less because you already have some of the drug in your system.
What I'm curious about is whether you are feeling some improvement or not. Often it may seem minor and you have to watch for it but it is an indicator that the medication is starting to reach therapeutic levels.