Diseases indicated by weak position of the planets in the birth chart !! 
Sun - blindness , bones related issues , calcium and sunlight gives vitamin d essential for bones 
Also look at condition of the 5 th house since its natural ruler of 5th zodiac the 5 th sign 
Moon - mind related issue 
Ruler of 4 th zodiac and hence look at the condition of the 4 th house 
Also chest area and lungs issues are seen through moon
Mars - blood related issue , high blood pressure , bone marrow , blood cells 
Natural ruler of 1st and 8th house , hence look at the condition of 1 at and 8 th house 
Ketu acts like Mars hence similar diseases.
Venus - sexual diseases , dibetese , eye problems , eye sight along Wid planet sun.
Pancreas and secretion of insulin 
Natural ruler of 2 bd and 7 th house hence check the condition of these houses as well before taking any decision
Jupiter - throat , liver .
Natural ruler ship of 9 th and 12 th house 
Saturn , also known as old man in Vedic astrology 
Old age issues , legs , leprecy, alcer , poison and cancer .
Natural ruler of 10 th and 11 th house 
Rahu acts like Saturn hence similar diseases.
Astrology chart can indicate the diseases but we as humans and top of the creation must meditate on gods name and get godly strength to deal with the health related issues 
And medical science research has made a lot of medical treatments to deal with these issue . 
Prevention is better then cure.