Deviation from the normal MCHC level is generally because of an underlying disease. Hence, depending upon the underlying medical condition, medications or dietary changes would be initiated by the doctor. For example, a low MCHC level is associated with iron deficiency anemia. Your doctor would suggest iron and vitamin B12 supplements or foods rich in iron and vitamin B12. Some foods rich in iron include spinach, peas, beans, seafood, red meat, etc. Food rich in vitamin B12 includes bananas, salmon, sweet potato, spinach, etc.
Similarly, treatment of high MCHC levels also depends on the underlying medical condition. Corticosteroids are mostly prescribed for treating autoimmune hemolytic anemia. In severe cases, immunosuppressive therapy (to suppress the immune system) or splenectomy (surgical removal of the spleen) would be performed.
Do not self-diagnose and treat these conditions. Consult your treating doctor for correct interpretation of the results and treatment.