You Shouldn't Mix This Medication With Vitamin C

Getting enough vitamin C is vital for your health and well-being. It serves as an antioxidant, helping to protect against cell damage and potentially reducing your risk of certain cancers. Vitamin C also promotes the immune system and helps the body make collagen, a protein that helps heal wounds, according to the National Institutes of Health (NIH). Men and women who aren't smokers need at least 90 mg and 75 mg of vitamin C per day, respectively, per NIH, but they should also be sure to not go beyond the recommended daily intake, as too much vitamin C can cause diarrhea, nausea, and stomach cramps.

However, some people need to take caution in how they get their vitamin C. Ascorbic acid (vitamin C) supplements can be effective in certain situations, but the NIH warns that they may interfere with certain medications and treatments, including chemotherapy and radiation therapy for cancer, and niacin when taken in combination with a statin for heart health. 

Vitamin C and fluphenazine

Verywell Health explains that vitamin C supplements can reduce the concentration of fluphenazine (an antipsychotic drug) in the blood, rendering the medication less effective. They might have a similar effect on chemotherapy drugs. According to Healthline, vitamin C can increase the acidity levels of your urine, leading you to excrete more or less of certain drugs than you would have otherwise, resulting in decreased effectiveness of prescribed medications.

The NIH notes that most people already get enough vitamin C and don't need supplements and that even if you're low in vitamin C, you should ideally get most or all of your vitamin C from food and drinks instead. On the other hand, some people take vitamin C supplements because their bodies have trouble absorbing the vitamin. If that's you, then the National Library of Medicine recommends discussing your medicines and all possible supplements with your doctor. That way, your doctor can know to monitor you carefully, advise you on how to minimize side effects, or even change your prescription if necessary. According to the NIH, consulting a doctor before taking vitamin C supplements is especially important for people being treated for cancer.