The heroin abuser’s nervous system becomes accustomed to accommodating chronic exposure to the drug, which is an opioid. Therefore, during heroin detoxification excruciating
withdrawal symptoms are ubiquitous.
Withdrawal symptoms begin within 12 hours of not using and peak after two to four days. The symptoms include: nausea, anxiety, diarrhea, abdominal pain, insomnia, chills, sweating, sniffing, sneezing, weakness and irritability. So I would say that yes, throwing up is normal.