Serum creatinine may also be increased in the following conditions: Use of angiotensin-converting enzyme (ACE) inhibitors and angiotensin IIreceptor blockers (ARBs) Consumption of large amounts of meat Use of some drugs (cimetidine, trimethoprim, cefoxitin, flucytosine) ACE inhibitors and ARBs reversibly decrease glomerular filtration rate (GFR) and increase serum creatinine because they vasodilate efferent more than afferent glomerular arterioles, mainly in people who are dehydrated or are receiving diuretics.