<s>[INST] i read some where that the body decreases in production of a certian chemical which may cause increase in blood pressure in the evening?  Do you know what it is...or can you tell me what may cause increase in blood pressure in the evening? Even on bld pressure meds my bld pressure sky rockets at night. [/INST] hi XXXXXXX if u have increased BP in evening that is not normal but u should b sure about it n to b sure u have to do few things- is you BP machine is working fine- have you not done any physical exertion before checking ur BP- you don't have fever now if everything told above all are not with u and ur BP is high in the evening then u have to compare it with the morning BP n do it in a routine n make flow chart with time n dateincreased BP in evening can be due to-kidney disease -diabetes - nervous system problems - thyroid problems- cardiovascular disease n other contributing factors are:-night duties- tobacco/ caffeine use-stress- anxiety </s>