If you are currently being treated with any of the following medications, you
should not use vitamin C supplements without first talking to your healthcare
Aspirin and Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)
Very limited research suggests that vitamin C may protect the
stomach and intestines against injury from NSAIDs such as ibuoprofen. On the
other hand, high doses of vitamin C (equal to or greater than 500 mg per day)
may raise the blood levels of aspirin and other acidic medications.
Vitamin C may decrease excretion of
acetaminophen (a medication sold over the counter for pain and headache) in the
urine, which may increase blood levels of this medication.
Animal studies suggest that vitamin C may
amplify the effects of furosemide, which belongs to a class of medications known
as loop diuretics.
Beta-blockers for high blood pressure
Vitamin C may decrease
the absorption of propranolol, a medication that belongs to a class known as
beta-blockers used for high blood pressure and other heart-related conditions.
If taking vitamin C and a beta-blocker, therefore, it is best to take them at
different times of the day.
Cyclosporine, a medication used for the treatment
of cancer, may reduce blood levels of vitamin C.
Nitrate Medications for heart disease
The combination of
vitamin C with nitroglycerin, isosorbide dinitrate, or isosorbide mononitrate
reduces the occurrence of nitrate tolerance. Nitrate tolerance is when the body
builds up a tolerance to the medicine so that it no longer has its desired
effect. People taking nitrate-containing medications generally follow a 12 hours
on, 12 hours off schedule to avoid this tolerance. Studies suggest that taking
vitamin C along with nitrate medications may reduce the development of this
There is some evidence that taking vitamin C with
the antibiotic tetracycline may increase the levels of this medication.
There have been rare case reports of vitamin C
interfering with the effectiveness of this blood thinning medication. In recent
follow up studies, no such association has been found with doses of vitamin C up
to 1,000 mg per day. Because of these much earlier reports, however, some
conservative clinicians suggest not exceeding RDA values of vitamin C (see
earlier section entitled How To Take It). Whether taking recommended dietary
amounts or larger quantities of vitamin C, anyone on warfarin must have their
bleeding time measured regularly and followed closely using a value called an
INR, measured at your doctor's office. If you take this blood thinner, any time
you make a change to your diet, medications, or supplements, you must notify