Hello, Thank you for your query. I understand your concerns. For a person who has been a walker and a runner, your difficulty in walking a very short distance and walking up flight of stairs is concerning. Do you have any other symptoms in addition to tiredness and shortness of breath? Like for e.g. do you have any palpitations (fast heart beat), swelling of feet, any loss of weight or gain in weight, increased thirst, increased hunger, lack of appetite, any blood in your urine or stool, any chronic cough etc.? There are quite a few causes for shortness of breath and tiredness – heart failure, arrythmias ( disorders of heart beat), diabetes, anaemia, kidney problems, thyroid problems etc, can all cause tiredness and breathlessness. I would advise you to see your doctor. He would run some blood tests like complete blood picture (to check for anaemia), serum creatinine and urea, blood glucose levels, Thyroid function tests, Liver function tests, Chest X ray, ECG etc. Based on his examination findings and the results of these tests he may ask for further investigations. Once your doctor identifies the causative factor for your symptoms he would be able to treat you. For e.g. if you have been found to have thyroid problems, then appropriate treatment of the thyroid disorder will improve your tiredness and breathlessness. I wish you a speedy recovery. I hope this answer has been helpful to you. Regards Dr Sunita Sayammagaru