Background. Sufficiently high levels of homoarginine (hArg) in the blood are associated with the lower risk of all-cause mortality. The relationship between the level of hArg and the availability of iron for energy metabolism and oxygen transport has not yet been evaluated. Objective. The aim of the study was to assess the association of known biochemical parameters, including the levels of amino acids, iron, blood hemoglobin, with hArg levels in patients with arterial hypertension (HTN) and other cardiovascular diseases (CVD). Design and methods. The study included 86 cases (33 men and 53 women) aged 60 (46–67) years old without folic acid and vitamin B12 deficiencies out of a total of 105 examined patients with HTN. Along with routine clinical trials, the plasma concentrations of amino acids: citrulline, arginine, serine, methionine (Met), lysine, hArg, and total homocysteine (tHcy) were studied. The feature associations were investigated in the procedure of multiple linear regression analysis. Results. In 30 % of cases, iron deficiency was observed, and the level of hArg was significantly reduced in more than half of the patients. No association of hArg levels with metabolites involved in transmethylation (Met and tHcy) was found. On the contrary, its significant association with iron assessments was found. Correlations of iron levels with the levels of other amino acids were not found. The best delineation of high and low iron levels according to the ROC-analysis corresponds to a hArg value of 1,55 µM (56 % sensitivity and 92 % specificity), which is very close to the 1,61 µM hArg value calculated from the iron reference cutoff (13 µM) in regression model. Conclusions. Iron deficiency to provide energy metabolism often accompanies CVD and is accompanied by a drop in hArg levels below 1,6 μM. Thus, the hArg level becomes important not only for assessing cardiovascular risk, but also as a parameter of the iron level effect on energy metabolism.