I just learned that when heroin use becomes regular, tolerance is developed. The more common for a person to use it on a daily basis, for example, will make a user tolerant and resorts to higher doses later.
The other day I saw this series in Nat Geo – Hard Time Judgment Day. One of the prisoners that was interviewed was a heroin addict and despite the growing tolerance, he did not seek heroin treatment. He got addicted for more that resulted for him landing in jail and he was implicated in a murder crime inside a house where they were supposed to do the session.
The crime happened while he was very high, and he was still when he was brought to jail the first time. He chose to be put on trial instead of admitting a guilty plea because he believed he did not participate in the crime. He was acquitted (after three years in prison) and I bet it is a better heroin treatment to stay in jail knowing that you are not guilty.