How safe is safe blood? Well, you could store your own blood between four to six degrees centigrade for your future use. But only for 35 days. And regulations allow donating blood only once in three months. So that option is not too practical. The Enzyme Linked Immuno Sorbet Assay (ELISA) test for AIDS is reliable. Or is it? Assume that it is carried out by technically sound experts. Even then, the HIV virus might take about six months, or more, to come to a detectable limit of concentration. And the Hepatitis B virus about 45 days. This is called the Window period—when the virus could well be incubating in the blood that tests negative for HIV or Hepatitis. The Rapid ELISA test, carried out in many non-metro blood banks shows false negativity, say experts. And the P24 test which could detect the virus within the space of 15 to 20 days is hardly done. But the unlucky may get blood which has been infected by the virus just two days before the test. Of course, you could freeze your blood forever on your next trip abroad. But few can afford to go abroad or freeze blood there. Or, for that matter, to buy blood here.