It is very common to feel weak after chickenpox; this is known as post-viral fatigue. Your body has spent significant energy fighting off the virus, leaving your immune system and energy reserves temporarily depleted. To recover, focus on plenty of rest, hydration, and a nutrient-rich diet. For supplements, a daily Multivitamin containing B-complex (for energy metabolism), Vitamin C, Vitamin D, and Zinc can help rebuild your immunity and strength. Avoid self-medicating with antivirals. If the weakness persists for more than a few weeks or is accompanied by a high fever, please consult your doctor for a personalized evaluation.