Side effects to some ingredients of high-dose pyridoxine hydrochloride (which is injected into the vein) are possible. Vitamin B6 may cause low blood pressure. Caution is advised in people with blood pressure disorders or in those taking drugs or herbs and supplements that lower blood pressure.Vitamin B6 may affect blood sugar levels.Caution is advised in people with diabetes or low blood sugar, and in those taking drugs, herbs, or supplements that affect blood sugar.ide Effects and Warnings. Vitamin B6 is likely safe when taken by mouth in recommended daily intake amounts. The recommended daily intake of vitamin B6 is as follows for adults: 1.3 milligrams in men and women ages 19-50; 1.7 milligrams in men aged 51 and older; and 1.3 milligrams in women aged 51 older.