I just checked Google AI, and here is what it said about fatigue from switching Kevzara injections from 2 to 3 weeks:

Potential Causes of Fatigue
- Subtherapeutic Drug Levels: The standard, studied dose for PMR is 200 mg every 2 weeks. Extending the interval to 3 weeks may drop the medicine level in your body too low to fully suppress the inflammatory proteins (IL-6) that cause systemic exhaustion.
- Early PMR Flare: Fatigue is often one of the very first warning signs of a breakthrough PMR flare, frequently arriving before or alongside stiffness and pain in the shoulders, neck, or hips.
- Steroid Taper Interaction: If you are simultaneously reducing your corticosteroid (prednisone) dose, your adrenal glands may also be struggling to catch up with cortisol production, compounding the wear-off fatigue.