Most medications do not prevent you from donating blood. Common medications such as those used to control blood pressure, birth control pills and over-the-counter medications do not affect your eligibility. If you have recently taken antibiotics, you must have completed the course prior to donating.
Yes, a tooth infection can cause a headache. Also, be aware that certain sinus conditions can mask as tooth problems.
If the infection is bad enough and it is in the nerve of your tooth, your immune system will kick in and tell your body that there is something wrong and that you need to get it fixed. Vertigo /dizziness, throbbing, lingering tooth aches and pain that wakes you up at night are the symptoms.