Yes, vitamin C supplements may interact with certain medications. This includes aspirin, acetaminophen, aluminum-containing antacids, barbiturates and nitrate medications for heart conditions. Vitamin C can also potentially affect estrogen levels when taken with oral contraceptives or hormone replacement therapy. It may also interact with certain antibiotics, protease inhibitors and blood thinners like warfarin. Always check with your healthcare provider before starting any new vitamin C supplements. This is especially important if you take medications.