Hi Would like to know your parents age, detailed history on health and also any family history There is no one blood test which can detect cancer But for commonly occuring cancers eg: breast , cervix in women , prostate in men certain screening programmes are available which people can start after 40-45 yrs Having said that these tests will help in early diagnosis so that the cure rates will be better You can consult for further details

You can't detect every cancer by blood tests. More over blood tests are only screening tests which can only help in detecting cancer if symptoms are present for a particular type of cancer. Without any symptoms, they may give false positive results. Please tell us for what type of cancer your relative was tested positive

Not all cancers have screenings test recommended for people without symptoms . Only those cancers which will benefit treatment if detected early are considered for screening . According to your age , only recommended screening test you should undergo is Pap smear once in every 3 years , which you should be doing irrespective of marital / sexual history . Which will screen for cervical cancer . After age 30 you can combine this HPV DNA testing , if both are negative once in 5 year test are enough . Other than this no cancer screening test is recommended at your age . If you are having any specific symptoms please do get back to me with that symptom so that I can suggest specific for any cancers .