Introduction Injecting Drug Users in India are at the duel risk of needle sharing and risky sexual behaviour, becoming more vulnerable to STI and HIV. Although injecting drug users constitute a risk group in themselves, there is also an overlap between drug addiction and those involved in sex work. Individuals who fall into both categories are therefore particularly vulnerable to HIV and are perhaps doubly stigmatised. Thus, studying the interface of injecting drug use and risky sexual behaviour is important to curb the pace of STI/HIV epidemic among IDUs.

Methods Data were obtained from two rounds of integrated biological and behavioural assessments (IBBA) conducted in 2006–07 and 2009–10 where 2,075 IDUs in round-1 and 1977 in round-2 were sampled. Data from both rounds were pooled. Bivariate and multivariate analysis were used for the study.

Results Data from 4052 IDUs from 6 districts of Manipur, Nagaland, and Maharashtra, were analysed. The mean age of IDUs in round-1 was 26 years and 29 years in round-2. The majority of the IDUs were illiterate, unmarried, employed in two consecutive rounds. IDUs’s duration between first drug use to first injecting drug use ≥2 years were 14 times higher during round-2. HIV and any STI symptoms in the round-2 show the declining pattern. IDUs having the main regular partner and shared needle/syringe were less likely to consistency in condom use with different type of female partners across the rounds. Logistics regression analysis of experienced any STI symptom in the past 1 year indicate that IDUs, literate (AOR=1.878, p<0.10), age at first injecting drugs 26 and above (AOR=2.192, p<0.05) and sharing needle/syringes in the past month (AOR=2.218, p<0.01) were significantly more likely than their counterparts. IDUs, ≥30 years (15.951, p<0.01), literate (3.415, p<0.01) and shared needle/syringes in the past one month were significantly more likely to have HIV.

Conclusions Harm reduction and needle exchange program should also focus on the risky behaviour of injecting drug users through peer-based approach.