Herbal preparations recommended in the treatment protocols for metabolic disorders are highly effective and less toxic than chemically synthesized ones. Plants of the Lamiaceae family, in particular Lavandula angustifolia, are known and widely used in the treatment and prevention of many diseases in humans and animals. In a 30-day experiment on model animals was studied the effect of dry herb narrow-leaved lavender on the rate of weight gain, metabolic parameters and the morphofunctional state of the heart, lungs, liver and kidneys. For this, two groups of white laboratory rats (n=7) consuming a high-fat diet for 30 days were formed. The experimental group was additionally given 5% of crushed dry lavender herb as part of the diet. We weighted the animals, calculated the average daily weight gain and at the end of the experiment determined the biochemical parameters of the blood, as well as assessed the macroscopic and microscopic changes in the internal organs. It was established that the addition of lavender to a high-fat diet led to increase in the average daily weight gain, and a significant increase in the absolute mass of the heart and liver compared to the control group. Among the biochemical parameters of the blood, the activity of alkaline phosphatase, as well as the level of total cholesterol and low-density lipoprotein cholesterol, increased significantly. A high-fat diet caused the development of granular degeneration in the kidneys, granular-fatty one in the liver, and the supplementation of the diet with lavender did not improve this condition.