What is Vitamin C: Uses, Warnings & Interactions

Updated May 14, 2025  •  Published Dec 30, 2020

Vitamin C (ascorbic acid) is a vital nutrient found in foods and supplements. The body needs vitamin C to synthesize protein, collagen, and many of the chemicals that pass signals between nerves. Vitamin C is also needed as an antioxidant and to absorb iron from plant foods. Because the body doesn’t make vitamin C, foods are our only source of this nutrient. Not only is vitamin C widely available as tablets, capsules, or powder for dietary supplementation, but it is also used in cough drops, skincare products, and toothpaste.

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Vitamin C overview

BRAND NAMES:

  • Ascor (injection), Emergen-C (tablets, powder), Ester-C (tablets), Infini-C (tablets), Vasoflex HD (tablets)

Generic Names:

  • Vitamin C

Uses:

  • Used to supplement the diet, treat vitamin C deficiency, improve immune system function, or enhance skin health and appearance

Therapeutic Classes:

  • Dietary supplement, nutritive agent, antioxidant, cosmeceutical (topical), skin lightening agent (topical)

Forms:

  • Tablet, chewable tablet, capsule, gummies, timed-release tablet, timed-release capsule, powder (crystals), liquid, injection, skin cream, facial serum

How it’s taken:

  • By mouth, on the skin

What is Vitamin C used for?

Vitamin C has a variety of applications:

  • Vitamin C tablets, capsules, gummies, powder, or liquids are taken at home as a dietary supplement or they are prescribed by doctors to treat vitamin C deficiency.

  • High-dose vitamin C supplements are sold as immune boosters or remedies. 

  • Vitamin C cough drops are intended to boost the immune system while relieving cough. 

  • Vitamin C injections are typically used as an initial treatment for symptomatic vitamin C deficiency (scurvy) in children and adults who cannot take oral vitamin C. 

  • Topical vitamin C preparations (serum, cream, sunscreen) are widely used as dermaceuticals to improve skin appearance and are considered an essential component of daily skincare routines. 

  • Vitamin C is also commonly added to toothpaste to promote gum health.

What form(s) does Vitamin C come in

  • Tablet

    • 250 mg

    • 500 mg

    • 1,000 mg

    • 1,200 mg

    • 2,000 mg

    • 3,000 mg

  • Capsule

    • 125 mg

    • 250 mg

    • 500 mg

    • 1,000 mg

    • 1,700 mg

    • 2,000 mg

  • Gummies

    • 125 mg

    • 250 mg

    • 500 mg

    • 1,000 mg

    • 2,000 mg

  • Oral powder or crystals (per serving or packet)

    • 250 mg

    • 500 mg

    • 2,000 mg

    • 2,032 mg

    • 3,000 mg

  • Timed-release tablet

    • 500 mg

    • 1,000 mg

  • Timed-release capsule

    • 500 mg

    • 1,000 mg

  • Liquid

    • 45 mg

    • 50 mg

    • 63 mg

    • 100 mg

    • 250 mg

    • 500 mg

    • 1,000 mg

    • 2,000 mg

  • Skin cream

    • 10%

    • 15%

    • 20%

    • 25%

  • Facial serum

    • 10%

    • 15%

    • 16%

    • 20%

    • 25%

    • 30%

  • Injection (Rx)

    • 500 mg/mL

What are common Vitamin C doses?

  • Recommended daily intake:

    • For adults and adolescents 19 years of age and older: 90 mg/day for men and 75 mg/day for women

    • For pregnant women: 85 mg/day 

    • For lactating women: 120 mg/day 

    • For children 14–18 years: 75 mg/day for boys and 65 mg/day for girls

    • For pregnant girls 14–18 years: 80 mg/day 

    • For lactating girls 14–18 years: 115 mg/day 

    • For children 9–13 years: 45 mg/day

    • For children 4–8 years: 25 mg/day

    • For children 1–3 years: 15 mg/day

    • For children 7–12 months: 50 mg/day (adequate intake)

    • For newborns to children up to the age of 6 months: 40 mg/day (adequate intake)

  • For vitamin C deficiency (scurvy): 

    • In adults: Up to 500 mg–1,000 mg/day by mouth OR 200 mg/day intravenous injection

    • In children: Up to 300 mg/day by mouth OR 50 mg/day (younger than one year) or 100 mg/day (1–11 years) intravenous injection

  • For skincare: Apply to the skin once per day in the morning or twice per day in the morning and evening

Common Vitamin C prescriptions

  • Vitamin C
    100 tablets bottle

  • Vitamin C
    100 tablets chewable bottle

  • Vitamin C
    118ml of 500mg/5ml bottle

  • Vitamin C
    300 tablets bottle

  • Vitamin C
    50 tablets chewable bottle

  • Vitamin C
    500 tablets bottle

  • Vitamin C
    500mg tablet

How to take Vitamin C

  • Follow the directions on the package or bottle when using vitamin C products. 

  • How to take vitamin C capsules, tablets, gummies, or powder:

    • Read and follow the directions on the label. Take the dose recommended on the label or advised by a healthcare provider.

    • Vitamin C supplements can be taken with or without food.

    • Swallow the tablet or capsule whole with a drink of water.

    • Chew vitamin C gummies or chewable tablets and then swallow.

    • Time-release vitamin C capsules and tablets must be swallowed whole with a drink of water. Do not crush, chew, or break them. Doing so may result in all the vitamin C in the tablet or capsule being released at once.

    • Mix vitamin C powder or crystals following the product’s instructions.

    • Store vitamin C tablets, capsules, gummies, or powder at room temperature. Avoid direct sunlight.

  • How to administer vitamin C drops or liquid to an infant or young child:

    • Read and follow the directions on the label.

    • Use the dosage guide that comes with the medicine or give doses as prescribed by a healthcare provider.

    • You usually do not need to shake the bottle before measuring a dose.

    • Use the calibrated dropper, oral syringe, or other dosing device that comes with the product to measure a dose.

    • Gently squirt the liquid into a baby’s cheeks or drop the liquid into a toddler’s mouth. An adult can take a dose directly in the mouth.

    • The dose can be mixed with foods or formula/expressed milk in a baby bottle.

  • How to apply vitamin C cream or serum:

    • Read and follow the directions on the label.

    • Vitamin C cream or serum is usually applied in the morning but can be applied in the morning and evening.

    • Cleanse the skin before applying vitamin C cream or serum.

    • It’s best to apply vitamin C and let it soak into the skin before applying moisturizer, other skincare products, or cosmetics.

    • Do not let vitamin C serum or cream come in contact with your eyes, lips, or nose.

    • Store vitamin C serum or cream in a cool dry place away from direct sunlight. Do not freeze.

What to do if you miss a dose of Vitamin C

  • Take a missed dose when remembered.

Vitamin C contraindications

  • You should not use vitamin C products if you have had an allergic reaction to ascorbic acid or any of the ingredients in the product.

Vitamin C warnings

  • Check with your healthcare provider before taking vitamin C supplements if you are pregnant, breastfeeding, or taking any medications.

  • Some people should avoid taking large doses of vitamin C supplements if they have certain medical conditions, such as:

    • Kidney stones

    • Sickle cell anemia

    • G6PD deficiency (a blood disorder)

    • Thalassemia (a blood disorder)

    • Hemochromatosis (a genetic disorder that causes iron overload in the body)

  • Tell any healthcare provider or other healthcare provider if you’re taking vitamin C supplements. Ascorbic acid can interfere with several important blood or urine tests.

  • Some vitamin C products—especially chewable tablets, gummies, powder, cough drops, or liquid—may contain aspartame. People with phenylketonuria should avoid these products because of potentially serious side effects.

  • People on a low-sodium diet should avoid taking vitamin C or any multivitamins containing sodium ascorbate as the active ingredient. People on a low-sodium diet should take vitamin C supplements containing ascorbic acid.

  • Vitamin C cream or serum should only be used on the skin. Do not ingest these products. 

  • Vitamin C skincare products are not recommended for use in children.

Vitamin C interactions

  • Talk to a healthcare provider before taking vitamin C supplements if you’re taking any medications.

  • Tell any healthcare provider prescribing new medications that you are taking vitamin C supplements.

  • High doses of vitamin C may cause problems in people taking:

    • Acetaminophen

    • Chemotherapy drugs

    • Birth control pills

Vitamin C side effects

Serious side effects

Most vitamin C serious side effects are due to either allergic reactions or taking large doses. Talk to a healthcare provider if you notice any signs or symptoms of a possible serious side effect, including:

  • Sharp pain in the lower back or sides, blood in the urine, trouble urinating, pain when urinating

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing

Less serious side effects

  • Nausea

  • Stomach upset

  • Diarrhea

  • Tingling (topical vitamin C)

Sources:

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