Background and Objective: Injection-site pain and bruising associated with subcutaneous injection of Heparin is one of the physical and psychological discomforts in patients. This study aimed at determining the effect of injection duration on the size of bruising and the severity of injection pain.

  Material and Methods: This quasi-experimental study was designed on 119 patients hospitalized in Panje Azar teaching center in Gorgan, 2009. For each patient, two subcutaneous injections of 10 and 30 seconds were performed with a 12-hour interval. Data collection was carried out using a researcher-made checklist that consists of two sections, demographic characteristics and a section to record the extent of bruising and pain intensity. The Extent of bruising was measured using clear flexible ruler within 48-72 hours and pain intensity by visual analog scale (VAS) immediately after Heparin injection. Data were analyzed using SPSS- 16 by central tendency and statistical tests.

  Results: The Findings show that 10-second injection in comparison to 30-second injection is more effective in increasing the exent of bruising and pain intensity. There is significant difference between the two methods (P<0.05).

  Conclusion: The duration of subcutaneous injection has an effect on bruising extent and the pain following the administration of Heparin in hospitalized patients. The findings can be used in clinical setting and nursing education.