In order to determine if the Chinese herbal medicine, Double P II (modified Da Huo Luo Dan/mDHLD), causes adverse clinical effects on serum biochemical parameters and complete blood counts (CBC), a controlled and randomized study was conducted. Ten healthy, intact female, middle-aged, beagle mixed breed dogs were randomly divided into placebo control (CG) (n = 5) and mDHLD study (SG) (n = 5) groups. A 4-week washout period was followed by a 9-day drug acclimation period, then a 4-week mDHLD or placebo trial was completed. Placebo capsule or mDHLD was dosed at 0.5 g (1 capsule) per 9 kg rounded to the nearest 0.5 g dose. Jugular venipuncture samples were collected on Days 0 and 9, and then weekly for 5 weeks. Serum chemistry profiles and CBC were performed for each dog immediately after collection. The mean corpuscular volume of CG was significantly different from baseline at multiple time points. The phosphorus was significantly higher in CG compared to SG at day 37. Serum calcium, total protein, albumin, and globulin all showed statistically significant decreases for SG and CG, compared to baseline values at varying time points. There were no statistically significant hematologic differences between SG and CG. There were statistically significant, but not clinically significant, differences in biochemical parameters between groups at one time point. Animals showed no negative clinical signs during the trial. This study showed no overt adverse clinical effects of mDHLD at the recommended dose and duration in otherwise healthy dogs. Further large-scale studies are warranted to determine safety for long term use of mDHLD in dogs with comorbidities.