Hello and Welcome to ‘Ask A Doctor’ service.
I have reviewed your query and here is my advice.
It may be due to common causes include diuretic use, diarrhea,
heart failure, liver disease, renal disease, and the syndrome of inappropriate ADH secretion (SIADH) etc. Please get Serum Na+, potassium, chloride, and bicarbonate,plasma osmolality,
serum creatinine,blood urea nitrogen,blood glucose,
urine osmolality,serum uric acid,serum cortisol,
thyroid-stimulating hormone and plasma AVP then consult your physician he will examine and treat you accordingly.
Hope I have answered your query.
Let me know if I can assist you further.