For me dizziness upon standing is a migraine symptom. It does seem to be a blood pressure drop; if I tighten my leg muscles (quads) it usually stops. Eating also helps, which is one reason I gained 10 lbs last year . But I've always felt better within minutes, not hours.
In your situation I don't know if I would wait a week to see a doctor.
- Gray 2010 carbon WSD road bike, Rivet Independence saddle
- Red hardtail 26" aluminum mountain bike, Bontrager Evoke WSD saddle
- Royal blue 2018 aluminum gravel bike, Rivet Pearl saddle
Gone but not forgotten:
- Silver 2003 aluminum road bike
- Two awesome worn out Juliana saddles