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Extreme fatigue could be due to anemia, diabetes, hypothyroidism, or due to kidney or liver problems. Another possibility is sleep disturbances (like sleep apnea, imbalance of rapid eye and non rapid eye movement sleep etc.). You may sleep your customary 7-8 hours and yet feel fatigued. You need sleep studies to rule this out. Other possibilities are chronic fatigue syndrome, depression, low Vit B12, low iron, low calcium, sodium and potassium. Hyperthyroidism too causes increased sweating and tiredness. It can also be due to menopause so get female hormone panel including LH, FSH, prolactin, estrogen, progesterone done. Do discuss this with your doctor and get yourself examined A comprehensive investigation is required keeping all the points in mind. Hope this helps. Take care!
Doctornee outlined the possibilities.
It is also possible for two problems to be existing at the same time.
You need to get to a facility where they will run a series of diagnostic tests. Sometimes the family physician is not prepared to do this. Don't wait too long. You don't have an "emergtency" but if you let these problems go they tend to cascade.
When you make your appointment, be prepared to state your symptoms, the date of onset, and provide a "time-line". Tell them if the symptoms get worse after eating a meal or at a particular time of the day. Write all your symptoms down on a piece of paper before you make the appointment. Tell them if the tymptoms have been getting progessively worse, or have remained the same. Bring all your medications.