The study concerned the determination of the influence of various manufactured mineral-plant additives, based on humic and calcium raw materials and dried herbs, lucerne and glycerol, on the content of Ca, P, Mg, K, Na, Cl and Cu, Fe, Zn in the blood serum of Lohmann Brown (LB) laying hens housed in a deep litter system. Five groups (20 hens in each) were formed, and they were fed using a standard mixture (group C) and ones enriched (3% share) in the following preparations: A - herbal-humic, B - humic-herbal, C - humic-lucerne, D - glycerol-humic. Blood for examinations was collected twice; at the peak of the laying period (phase I), and in further stages of laying production (phase II). The applied mineral-plant feed additives did not unequivocally affect the differentiation of the value of blood serum mineral indices; however, the glycerol-humic preparation significantly increased the level of Ca, P in phase I, and Cu, Zn in phase II. Generally, higher contents of Ca, P, Mg, K and Cu, Fe and Zn were noted in phase II of the laying period, when compared to phase I. The results of this study may suggest the acceptance of the following values as initial data for further research on establishing of mineral indices reference values in laying hens’ blood serum. In phase I (peak of the laying period) and in phase II (further stage of laying period) they were: calcium 6.2-7.1 and 7.6-8.3 mmol/l, phosphorus 1.6-2.1 and 1.9-2.2 mmol/l, copper 3.7-5.1 and 5.0-7.1 µmol/l, iron 39-45 and 40-47 µmol/l, and zinc 37-43 and 39-47 µmol/l, respectively. The following values are proposed for the electrolytes during the entire laying period: sodium 147-149 mmol/l, potassium 4.6-5.2 mmol/l, chlorine 115-118 mmol/l.