New Delhi, Nov 21 : High haemoglobin levels can raise your risk of heart attack, stroke and blood clots, according to health experts. Known as polycythemia -- a condition where red cells increase in the human body due to abnormalities in the bone marrow. These excess cells thicken the blood, slowing its flow and can cause serious problems like blood clots. Other causes of polycythemia include smoking, diseases of the heart or lungs and living at high altitude for prolonged time periods. Haemoglobin levels of more than 16.5g/dL in males and 16g/dL in females is considered abnormal. High haemoglobin levels may be detected on routine blood tests and may not cause any symptoms. 'High haemoglobin levels should not be ignored as it can increase the risk of blood clotting and can sometimes lead to dangerous conditions like stroke, heart attack and blood clots in legs and abdomen,' said Dr Rahul Bhargava, Principal Director of Hematology and Bone Marrow Transplant, Fortis Memorial Research Institute, Gurugram. 'If high haemoglobin levels are detected on routine evaluation, a haematologist should be consulted for further evaluation. Secondary causes of polycythemia including obstructive sleep apnoea, diseases of heart and lungs should be looked for,' he added. Routine blood tests to detect haemoglobin levels include a peripheral smear, serum erythropoietin levels and JAK2 mutation study is necessary for routine evaluation. A bone marrow examination is also performed to determine the cause of polycythemia in selected cases. According to Dr. Neha Rastogi Panda, Senior Infectious Diseases Specialist at Fortis Memorial Research Institute, Gurugram, 'High haemoglobin may also cause a variety of symptoms like frequent headaches, blurred vision, itching all over the body after a warm shower, painful and swollen joints'. 'It can also cause major problems like stroke, heart attack, blood clot in legs etc. Smoking should be avoided as it increases the risk of blood clotting. Diabetes and high blood pressure should be controlled as they are independent risk factors for stroke and heart attack. Adequate oral fluid intake should be maintained,' she added. Treatment of polycythemia includes removing blood from the body -- a process called phlebotomy, blood thinners like aspirin which helps prevent blood clotting and medicines like hydroxyurea which helps stop bone marrow from producing increased cells. /IANS