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What not to mix vitamin C with?

Vitamin C, also known as ascorbic acid, is an essential nutrient that plays many important roles in the body. It is important for the growth and repair of tissues, helps make collagen, enhances iron absorption, and acts as an antioxidant to protect cells from damage. Vitamin C is also key for immune system function and helps the body absorb other nutrients properly. It is a water-soluble vitamin, meaning excess amounts are excreted in urine.

Most people can safely take vitamin C supplements or get enough from foods like citrus fruits, peppers, broccoli and leafy greens. However, there are some important interactions and precautions to be aware of when taking vitamin C. Understanding what not to mix with vitamin C can help you avoid potential issues.

Medications that Interact with Vitamin C

There are several types of medications that can interact with vitamin C. Being aware of these interactions can help avoid problems.

Blood Thinners

Vitamin C supplements can interact with blood thinners like warfarin and increase the risk of bruising and bleeding. This is because vitamin C enhances the effects of warfarin and causes it to act more strongly as a blood thinner.

If you take warfarin or other blood thinning medications like clopidogrel or aspirin, talk to your doctor before taking vitamin C supplements. Make sure your doctor knows about any supplements you are taking so they can help monitor for interactions.

Blood Pressure Medications

Vitamin C may also interact with blood pressure lowering medications like ACE inhibitors. It can act as a diuretic itself and taking it in high doses could enhance the effects of these medications, potentially causing blood pressure to become too low.

Some examples of ACE inhibitors that vitamin C can interact with include lisinopril, enalapril, ramipril and captopril. If you take any medication to lower blood pressure, consult your doctor before taking vitamin C supplements to prevent unsafe drops in blood pressure.

Diabetes Medications

Vitamin C supplements can lower blood sugar, so taking high doses may interfere with diabetes medications. Vitamin C enhances insulin sensitivity and glucose metabolism.

People who take insulin or other diabetes drugs like glimepiride and metformin need to be cautious about taking high dose vitamin C supplements. Monitor blood sugar closely when combining the two.


Estrogen medications like birth control pills can potentially interact with vitamin C. Vitamin C might lower estrogen levels in the body and make birth control pills less effective.

Speak with your doctor before supplementing with vitamin C if you take any form of birth control containing estrogen, such as pills, patches or injections.


Taking vitamin C with fluoride supplements or fluoridated water can increase the risk of teeth staining and decay. Vitamin C increases fluoride absorption and ingesting both together creates optimal conditions for tooth enamel damage to occur.

If you take fluoride supplements, wait at least one hour before taking vitamin C to avoid this interaction. For fluoridated water, wait 30 minutes between drinking and taking vitamin C.

Chemotherapy Drugs

Some chemotherapy drugs like methotrexate depend on quickly dividing cells to be effective. Vitamin C is thought to encourage cancer cell division, potentially making methotrexate less effective.

Do not take high doses of vitamin C supplements without consulting your oncologist first if you are undergoing chemotherapy.

Other Supplements and Vitamins that Don’t Mix with Vitamin C

In addition to medications, there are some other supplements and vitamins that vitamin C can negatively interact with. Pay attention to these combinations:


Though vitamin C aids iron absorption, taking them together in high doses can cause gastrointestinal upset. Vitamin C increases iron absorption significantly, so too much iron with vitamin C can lead to iron overdose toxicity.

If supplementing with both iron and vitamin C, take them several hours apart. Only take high doses of both under medical supervision.

Vitamin B12

Vitamin C can make vitamin B12 less effective in the body by competing for absorption. Taking large doses of both could lead to vitamin B12 deficiency over time.

Separate your vitamin B12 and vitamin C supplements by several hours to avoid this negative interaction.

Vitamin E

Vitamin E requires fat for absorption, while vitamin C needs water. When you take them together, vitamin C ends up flushing out vitamin E before it can be properly absorbed.

Avoid taking vitamin C and vitamin E at the same time. Allow several hours between them if you want to take both.


Like with iron, vitamin C improves copper absorption. Too much copper can cause toxicity and taking high doses of vitamin C with copper supplements is not recommended.

Only take copper and vitamin C supplements together under medical guidance to avoid copper overdose.


Vitamin C may potentially cause mild increases in selenium excretion through urine. If supplementing with both, make sure you take selenium in the form of selenomethionine rather than selenium salts like selenate or selenite.

Selenomethionine is not as impacted by vitamin C and is the best form of selenium to take.


High doses of vitamin C can decrease zinc absorption and increase zinc excretion through urine. To prevent zinc deficiency, separate your zinc and vitamin C supplements by several hours.

Also, avoid taking vitamin C supplements for a prolonged period of time if you also take zinc.

Foods and Beverages to Avoid Taking with Vitamin C

Beyond supplements and medications, there are some foods and drinks that you should not consume at the same time as vitamin C:


Drinking alcohol is not recommended when taking vitamin C supplements. Alcohol increases the amount of vitamin C flushed out in urine, reducing its effectiveness.

If consuming alcohol, avoid taking vitamin C supplements for the next few hours. The vitamin C will not be properly absorbed.


Similar to alcohol, the phosphoric acid in sodas like cola can increase the rate of excretion of vitamin C. The soda ends up flushing out the vitamin before it can be utilized.

Avoid drinking soda and other carbonated soft drinks when you take vitamin C supplements or consume vitamin C-rich foods.

Coffee and Tea

Caffeine found in coffee, tea, and energy drinks can also interact with vitamin C, leading to increased vitamin C excretion through urine. Coffee and tea also contain polyphenols that can bind to vitamin C.

Have your coffee or tea separate from any vitamin C supplements or foods high in vitamin C to limit these negative impacts.

Raw Foods

Eating raw foods that contain vitamin C like citrus fruits, tomatoes, or peppers at the same time as cooked foods can decrease vitamin C absorption. Raw fruits and vegetables have enzymes that break down vitamin C.

For best vitamin C absorption from raw produce, consume these foods separately from cooked items.

Potential Side Effects of High-Dose Vitamin C

While vitamin C is generally safe at recommended daily amounts, taking extremely high doses may cause side effects like:

  • Kidney stones
  • Nausea, vomiting, heartburn
  • Abdominal cramps
  • Headache
  • Insomnia
  • Facial flushing

Very high dose IV vitamin C administered by a doctor may also carry risks like:

  • Dehydration
  • Blood clots
  • Fatigue
  • Leaky gut syndrome

Due to potential toxicity at high levels, the recommended upper limit for vitamin C is 2,000 mg per day for adults. Unless medically indicated under doctor supervision, avoid taking this amount regularly.

Key Takeaways on What Not to Mix with Vitamin C

Here are some key tips on what not to take or consume with vitamin C:

  • Do not take vitamin C with blood thinners like warfarin, aspirin, or clopidogrel.
  • Avoid combining vitamin C with ACE inhibitor blood pressure medications.
  • Do not take vitamin C supplements with insulin or diabetes medications.
  • Check with your doctor before taking vitamin C with estrogen medications like birth control.
  • Take vitamin C supplements one hour apart from fluoride supplements or fluoridated water.
  • Consult your oncologist before taking vitamin C with chemotherapy drugs like methotrexate.
  • Take iron supplements several hours apart from vitamin C to avoid toxicity.
  • Allow a few hours between taking vitamin C and other supplements like vitamin B12, vitamin E, zinc, copper or selenium.
  • Avoid consuming alcohol, coffee, tea, and soda when taking vitamin C.
  • Do not exceed 2,000 mg of vitamin C per day from supplements unless prescribed by your doctor.

The Bottom Line

Vitamin C is generally safe but can interact with and disable certain medications, supplements, and foods. Being mindful of what not to take vitamin C with allows you to gain its beneficial effects while avoiding problems.

Always let your doctor know about any supplements you take, including vitamin C. Avoid taking more than 2,000 mg per day and be cautious combining vitamin C with anything that may interact.

Paying attention to what you mix vitamin C with lets you harness its immune-boosting, antioxidant power safely.