The appropriate dosage of Vitamin D3 (Cholecalciferol 60000 IU) oral solution for a senior citizen should be personalized by a doctor based on vitamin D levels and health status.

• A common approach to treat deficiency is taking one 60000 IU dose once weekly for 6 to 8 weeks.
• After this, a lower maintenance dose may be advised to keep levels stable.
• Avoid self-medicating with high doses to prevent vitamin D toxicity.

Please consult a specialist such as an endocrinologist or geriatrician who can order blood tests (like serum 25-hydroxyvitamin D) and tailor the dosage safely. If you notice symptoms like nausea, vomiting, weakness, or frequent urination while on vitamin D, seek medical care promptly.