The success of taking HIV blocking medication is related to the timing of blocking, taking the blocking medication, taking the medication regularly, and whether high-risk behaviors persist. Once high-risk sexual behavior occurs, a history of high-risk exposure, it is important to go to the hospital as soon as possible to initiate post-exposure prophylaxis as early as possible. Usually, if the blocking drug can be taken within 2 hours, it has a very high chance of blocking, almost 100%. However, the effectiveness of blockade decreases with time. In general, try to take the blocking medication within 24 hours, but not longer than 72 hours. And the drug is not resistant to the infected virus, and the vast majority of them can be successfully blocked. However, the success rate is not 100%, there are some factors that will affect the success of the blockade, for example, a small number of patients take a combination of drugs, may happen to be resistant to the HIV virus, then the blockade may fail. Therefore, once you suspect HIV infection, you should go to the hospital, consult your doctor and take the blocking medication as soon as possible.