Vitamin C

NatMed Pro rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.

Effective for …

• Vitamin C deficiency. Taking vitamin C by mouth or injecting it as a shot prevents and treats vitamin C deficiency, including scurvy. Also, taking vitamin C can reverse problems associated with scurvy. Only a healthcare provider can inject vitamin C as a shot.

Possibly Effective for …

• Low levels of red blood cells in people with a long-term illness (anemia of chronic disease). Taking vitamin C supplements by mouth might help manage anemia in people undergoing dialysis.
• Irregular heartbeat (atrial fibrillation). Taking vitamin C by mouth or by IV before and after heart surgery helps prevent irregular heartbeat after heart surgery. IV products can only be given by a healthcare provider.
• Emptying the colon before a colonoscopy. A specific fluid containing vitamin C (MoviPrep, Salix Pharmaceuticals, Inc.) has been approved by the FDA for bowel preparation before a colonoscopy. Some bowel preparations involve drinking 4 liters of medicated fluid. If vitamin C is included in the fluid, only 2 liters are needed.
• Cataracts. Eating more vitamin C or taking vitamin C supplements by mouth might prevent cataracts. But it’s not clear if taking vitamin C supplements by mouth helps people who already have cataracts.
• Common cold. Taking 1-3 grams of vitamin C by mouth might shorten the course of a cold by 1 to 1.5 days. But taking vitamin C does not appear to prevent colds.
• Limb pain that usually occurs after an injury (complex regional pain syndrome). Taking vitamin C by mouth after surgery or injury seems to prevent complex regional pain syndrome from developing.
• Recovery from laser skin therapy. Applying a skin cream containing vitamin C might decrease skin redness after laser skin therapy for scar and wrinkle removal.
• Airway infections caused by exercise. Taking vitamin C by mouth before heavy physical exercise, such as a marathon or army training, might prevent upper airway infections that can occur after heavy exercise.
• High cholesterol. Taking vitamin C by mouth might reduce low-density lipoprotein (LDL or “bad”) cholesterol in people with high cholesterol.
• High blood pressure. Taking vitamin C by mouth might help lower systolic blood pressure (the top number in a blood pressure reading) by a small amount. But it does not seem to lower diastolic pressure (the bottom number).
• Lead poisoning. Consuming vitamin C in the diet seems to lower blood levels of lead.
• Reduced benefit of nitrate therapy that happens when nitrates are used all day (nitrate tolerance). Taking vitamin C by mouth seems to help drugs for chest pain, such as nitroglycerin, to work longer.
• Pain after surgery. Taking vitamin C by mouth or by IV might reduce pain during the first 24 hours after surgery. But it’s unclear if taking vitamin C by mouth can reduce pain during the first 6 weeks after surgery. IV products can only be given by a healthcare provider.
• Wrinkled skin. Applying skin creams containing vitamin C seems to improve the appearance of wrinkled skin. Apply a vitamin C patch also seems to help reduce wrinkles.

Possibly Ineffective for …

• Short-term swelling (inflammation) of the airways in the lungs (acute bronchitis). Taking vitamin C by mouth does not seem to have any effect on bronchitis.
• Asthma. Taking vitamin C by mouth doesn’t seem to prevent asthma or improve symptoms in people who already have asthma.
• Hardening of the arteries (atherosclerosis). Taking vitamin C by mouth does not seem to prevent atherosclerosis from becoming worse in most people with this condition.
• Bladder cancer. Taking vitamin C by mouth does not seem to prevent bladder cancer or reduce bladder cancer-related deaths.
• Heart disease. Taking vitamin C by mouth does not prevent heart disease or reduce death due to heart disease.
• Colon cancer, rectal cancer. Taking vitamin C by mouth does not seem to prevent cancer in the colon or rectum.
• Death of an unborn or premature baby. Taking vitamin C by mouth, alone or with other supplements, during pregnancy doesn’t prevent death of an unborn or premature baby.
• Fractures. Taking vitamin C by mouth does not seem to improve function, symptoms, or healing rates in people with a wrist fracture.
• A digestive tract infection that can lead to ulcers (Helicobacter pylori or H. pylori). Taking vitamin C by mouth along with medicines used to treat H. pylori infection doesn’t seem to get rid of H. pylori faster than taking the medicines alone.
• A group of inherited disorders that leads to muscle weakness and numbness in the arms and legs. Taking vitamin C by mouth for one or two years does not seem to prevent nerve damage in people with these disorders.
• Eye damage in people taking drugs called interferons (interferon-related retinopathy). Taking vitamin C by mouth does not seem to prevent eye damage in people receiving interferon therapy for liver disease.
• Cancer of the white blood cells (leukemia). Taking vitamin C by mouth doesn’t seem to prevent leukemia or death due to leukemia.
• Lung cancer. Taking vitamin C by mouth, alone or with vitamin E, doesn’t seem to prevent lung cancer or death due to lung cancer.
• The most serious type of skin cancer (melanoma). Taking vitamin C by mouth, alone or with vitamin E, doesn’t prevent melanoma or death due to melanoma.
• Miscarriage. Taking vitamin C by mouth, alone or with other supplements, during pregnancy does not prevent miscarriage.
• Death from any cause. Taking vitamin C by mouth along with other antioxidants does not seem to prevent death.
• Pancreatic cancer. Taking vitamin C by mouth together with beta-carotene plus vitamin E does not seem to prevent pancreatic cancer.
• A pregnancy complication marked by high blood pressure and protein in the urine (pre-eclampsia). Taking vitamin C by mouth with vitamin E during pregnancy does not prevent high blood pressure and protein in the urine during pregnancy.
• Preterm birth. Taking vitamin C by mouth, alone or with other supplements, during pregnancy does not prevent preterm birth.
• Prostate cancer. Taking vitamin C by mouth does not seem to prevent prostate cancer.
• Skin damage caused by radiation therapy (radiation dermatitis). Applying a vitamin C solution to the skin does not prevent skin problems caused by radiation treatments.
• Infants with birth weight below the 10^th percentile. Taking vitamin C by mouth, alone or with other supplements, during pregnancy does not reduce the chance of giving birth to an infant with a low birth weight.
• Stillbirth. Taking vitamin C by mouth, alone or with other supplements, during pregnancy does not reduce the chance of having a stillbirth.

Probably Ineffective for …

• Coronavirus disease 2019 (COVID-19). Taking high-dose vitamin C by mouth does not seem to speed up recovery from COVID-19 in people who aren’t in the hospital. Giving vitamin C by mouth or IV to people who are in the hospital with severe COVID-19 might have some benefit, but more studies are needed to say for sure.
• Blood infection (sepsis). Giving vitamin C by IV with or without thiamine and/or a steroid does not reduce the risk of dying, organ damage, hospitalization duration, or the need for supportive treatment in people with sepsis.

There is interest in using vitamin C for a number of other purposes, but there isn’t enough reliable information to say whether it might be helpful.

When taken by mouth: Vitamin C is likely safe for most people. In some people, vitamin C might cause side effects such as stomach cramps, nausea, heartburn, and headache. The chance of getting these side effects increases with higher doses. Taking more than 2000 mg daily is possibly unsafe and may cause kidney stones and severe diarrhea. In people who have had a kidney stone, taking amounts greater than 1000 mg daily increases the risk of getting more kidney stones.

When applied to the skin: Vitamin C is likely safe for most people. It might cause irritation and tingling.

Special Precautions & Warnings:

Pregnancy and breast-feeding: Vitamin C is likely safe to take by mouth during pregnancy in amounts no greater than 2000 mg daily for those 19 years and older and 1800 mg daily for those 14-18 years old. Taking too much vitamin C during pregnancy can cause problems for the newborn baby. Vitamin C is possibly unsafe when taken by mouth in excessive amounts.

Infants and children: Vitamin C is likely safe when taken by mouth appropriately. Vitamin C is possibly unsafe when taken by mouth in amounts higher than 400 mg daily for children 1-3 years, 650 mg daily for children 4-8 years, 1200 mg daily for children 9-13 years, and 1800 mg daily for adolescents 14-18 years.

Alcohol use disorder: People who regularly use alcohol, especially those who have other illnesses, often have vitamin C deficiency. These people might need to be treated for a longer time than normal to restore vitamin C levels to normal.

Cancer: Cancerous cells collect high concentrations of vitamin C. Until more is known, only use high doses of vitamin C under the direction of your oncologist.

Chronic kidney disease: Long-term kidney disease might increase the risk of vitamin C deficiency. Vitamin C supplements might also increase the amount of oxalate in the urine in some people. Too much oxalate in the urine can increase the risk of kidney failure in people with kidney disease.

A metabolic deficiency called “glucose-6-phosphate dehydrogenase” (G6PD) deficiency: Large amounts of vitamin C can cause red blood cells to break in people with this condition. Avoid excessive amounts of vitamin C.

Kidney stones: Large amounts of vitamin C can increase the chance of getting kidney stones. Do not take vitamin C in amounts greater than those found in basic multivitamins.

Smoking and chewing tobacco: Smoking and chewing tobacco lowers vitamin C levels. People who smoke or chew tobacco should consume more vitamin C in the diet.

Acetaminophen (Tylenol, others)

Interaction Rating=Minor Be watchful with this combination.

The body breaks down acetaminophen to get rid of it. Large amounts of vitamin C can decrease how quickly the body breaks down acetaminophen. It is not clear if this interaction is a big concern.

Aluminum

Interaction Rating=Moderate Be cautious with this combination.

Aluminum is found in most antacids. Vitamin C can increase how much aluminum the body absorbs. However, it is not clear if this interaction is a big concern. Take vitamin C two hours before or four hours after antacids.

Aspirin

Interaction Rating=Minor Be watchful with this combination.

Aspirin is removed by the body through the kidneys and in the urine. Vitamin C might decrease how the body removes aspirin and could potentially increase the amount of aspirin in the body. But it’s not clear if this is a big concern.

Choline Magnesium Trisalicylate (Trilisate)

Interaction Rating=Minor Be watchful with this combination.

Vitamin C might decrease how quickly the body gets rid of choline magnesium trisalicylate. It is not clear if this interaction is a big concern.

Estrogens

Interaction Rating=Moderate Be cautious with this combination.

Vitamin C might decrease how quickly the body gets rid of estrogens. Taking vitamin C along with estrogens might increase the effects and side effects of estrogens.

Fluphenazine (Prolixin)

Interaction Rating=Moderate Be cautious with this combination.

Large amounts of vitamin C might decrease how much fluphenazine is in the body. Taking vitamin C along with fluphenazine might decrease the effectiveness of fluphenazine.

Indinavir (Crixivan)

Interaction Rating=Moderate Be cautious with this combination.

Taking large amounts of vitamin C along with indinavir might decrease how much indinavir stays in the body. It’s not clear if this interaction is a big concern.

Levothyroxine (Synthroid, others)

Interaction Rating=Moderate Be cautious with this combination.

Taking vitamin C along with levothyroxine might increase how much levothyroxine the body absorbs. This can increase the amount of levothyroxine in the body and increase its effects and side effects.

Medications for cancer (Alkylating agents)

Interaction Rating=Moderate Be cautious with this combination.

Vitamin C is an antioxidant. There is some concern that antioxidants might decrease the effects of some medications used for cancer. If you are taking medications for cancer, check with your healthcare provider before taking vitamin C.

Medications for cancer (Antitumor antibiotics)

Interaction Rating=Moderate Be cautious with this combination.

Vitamin C is an antioxidant. There is some concern that antioxidants might decrease the effects of medications used for cancer. If you are taking medications for cancer, check with your healthcare provider before taking vitamin C.

Niacin

Interaction Rating=Moderate Be cautious with this combination.

Taking niacin with vitamin C and other antioxidants can decrease the effects of niacin on good cholesterol levels. It is unknown if vitamin C alone decreases the effects of niacin on good cholesterol levels.

Salsalate (Disalcid)

Interaction Rating=Minor Be watchful with this combination.

Vitamin C might decrease how quickly the body gets rid of salsalate. Taking vitamin C along with salsalate might cause too much salsalate in the body, and increase the effects and side effects of salsalate.

Warfarin (Coumadin)

Interaction Rating=Moderate Be cautious with this combination.

Warfarin is used to slow blood clotting. Large amounts of vitamin C might decrease the effects of warfarin. Decreasing the effects of warfarin might increase the risk of clotting. Be sure to have your blood checked regularly. The dose of your warfarin might need to be changed.

Acerola: Acerola contains high levels of vitamin C. Don’t take large amounts of acerola along with vitamin C. This might give you too much vitamin C. Adults should not take more than 2000 mg vitamin C per day.
Chromium: Vitamin C might increase chromium absorption. Don’t take large doses of chromium and vitamin C together. It isn’t known whether separating the doses by several hours avoids this interaction.
Copper: High doses of vitamin C (1500 mg daily) can decrease copper levels in the blood. This interaction probably isn’t important except in people whose dietary intake of copper is low.
Grape: Taking vitamin C with grape seed might increase blood pressure in people with high blood pressure. It’s not clear why this happens.
Iron: Vitamin C increases the absorption of iron when taken at the same time. But taking a vitamin C supplement to improve absorption of iron from the diet or from supplements probably isn’t necessary for most people.
Rose hip: Rose hip contains high levels of vitamin C. Don’t take large amounts of rose hip along with vitamin C. This might give you too much vitamin C. Adults should not take more than 2000 mg vitamin C per day.
Vitamin B12: There have been concerns that vitamin C can lower vitamin B12 levels in the body. But vitamin C supplements don’t seem to affect levels of vitamin B12.

There are no known interactions with foods.

Vitamin C is an important nutrient. Fresh fruits and vegetables, especially citrus fruits, are good sources of vitamin C. The amount that should be consumed on a daily basis is called the recommended dietary allowance (RDA). For adult males, the RDA is 90 mg daily. For females 19 years and older, the RDA is 75 mg daily. While pregnant and breastfeeding, the RDA is 120 mg daily for people 19-50 years old. In children, the RDA depends on age.

Vitamin C is also available in supplements, combination products, liquids, lotions, creams, serums, sprays, and patches. Supplements have been used safely by adults in doses up to 2000 mg daily. Speak with a healthcare provider to find out what type of product and dose might be best for a specific condition.

Acide Ascorbique, Acide Cévitamique, Acide Iso-Ascorbique, Acide L-Ascorbique, Acido Ascorbico, Antiscorbutic Vitamin, Ascorbate, Ascorbate de Calcium, Ascorbate de Sodium, Ascorbic Acid, Ascorbic acid, Ascorbyl Palmitate, Ascorbyl Phosphate, Calcium Ascorbate, Cetyl Ascorbate, Cevitamic Acid, Chromium Ascorbate, Copper Ascorbate, Ferrous Ascorbate, Iron Ascorbate, Iso-Ascorbic Acid, L-Ascorbic Acid, Magnesium Ascorbate, Niacin Ascorbate, Niacinamide Ascorbate, Nicotinamide Ascorbate, Palmitate d’Ascorbyl, Phosphate Ascorbate, Potassium Ascorbate, Selenium Ascorbate, Sodium Ascorbate, Strontium Ascorbate, Vitamina C, Vitamine Antiscorbutique, Vitamine C, Zinc Ascorbate.