The effect of garlic on coagulation tests

Background and There are many reports on anti-thrombotic properties of garlic. Also, regarding the simultaneous consumption of garlic and Warfarine or non-steroid anti-inflammatory drugs (NSAIDs), some warning recommendations are published. The aim of present study was to evaluate the effects of garlic on coagulation tests, and in case of any demonstrative anticoagulation effect, the patients, particularly those with coagulation disorders, could be given appropriate advice on proper consumption of garlic. This was a clinical trial in which 50 volunteer students were selected based on information collected using appropriate questionnaires. The students were tested for coagulation assays including bleeding time (BT), clotting time (CT), prothrombin time (PT), partial thromboplastin time (PIT), clot retraction (CR), and platelets count (PC) before and after consumption of garlic. Data were analyzed using SPPS and T-test. The average values of tests obtained in two stages of experiment were further compared statistically. The results of our study on subjects (30 females and 20 males) with an average age of 21.7 years showed that there was no significant change in values obtained for CT, PT, PC and CR (p>0.05) following consumption of garlic. However, a significant increase in PTT values was found following consumption of garlic (the p values for samples collected after 24 hours and 4 hours were 0.001 and 0.012 respectively). There was also a significant difference (p=0.027) in BT 24 hours after garlic consumption. Regarding the results of similar tests among two genders, no significant difference was found. Following consumption of garlic, there was a significant increase in PIT and BT, the effect being more obvious after 24 hours. The data of present study regarding the inhibitory effect of garlic on platelet activities is consistent with those reported by some other researches which is also indicative of interference of garlic with PIT assays.