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Fatigue & tiredness
or weakness does occur when you have suffered fever like typhoid & malaria as they make you exhausted.Also you need to take anti-malarial for malaria & antibiotic for typhoid which cause drug induced gastritis
and generalised weakness.The dizziness
you get after standing up from the toilet seat is due to postural hypotension
.Please take enough water also add electrolyte powder to it ;you will feel better.As for nausea;vomiting you can ask your doctor to prescribe antacid & anti emetic.
Hope this answer is helpful to you.