Brief Answer:
Can be anemia or thyroid issues

Detailed Answer:
Hello dear welcome to Ask a doctor's service.
I read your query and here is my advice.
If you are having general weakness you may need to get further tested doing a total blood count with formula and iron levels.
Also get your thyroid checked doing thyroid hormone levels.
Sometimes iron deficiency anemia and thyroid imbalance may be the main reason for weakness

Hope I have answered the question.
Let me know if I can assist you further

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