Vitamin C (Ascorbic Acid)

Essential water-soluble vitamin and powerful antioxidant critical for immune function and collagen synthesis

Scientific nameL-Ascorbic Acid FormulaC6H8O6 Molecular weight176.12 g/mol CAS50-81-7

80 absorption score

9 safety / 10

10 USD per month

5 documented interactions

Check it against something

Evidence level A

Vitamin C (Ascorbic Acid) with:

99 out of 100

Works better together Compatible. Timing differs, so follow each supplement's own window.

Check it against your whole stack →

What it does

mechanism and evidence for each claim

Immune system enhancement

Reduces duration and severity of cold symptoms by 8-20%

Supports neutrophil function and antibody production Evidence A-grade 1-2 weeks

Collagen synthesis

Essential for healthy skin, bones, and connective tissue

Cofactor for prolyl and lysyl hydroxylases Evidence A-grade 4-8 weeks

Iron absorption enhancement

Increases non-heme iron absorption by up to 4x

Reduces ferric iron to absorbable ferrous form Evidence A-grade Immediate with meals

Antioxidant protection

Neutralizes free radicals and regenerates other antioxidants

Direct radical scavenging and vitamin E regeneration Evidence A-grade 2-4 weeks

Cardiovascular health

May improve endothelial function and blood pressure

Nitric oxide pathway support and endothelial protection Evidence B-grade 4-8 weeks

Others take these for the same thing

Same goal, different mechanism — check any of them against this one

Probiotics for Autoimmune Disease Support Gut health & immune modulation 10-100 billion CFU daily B 60% Turmeric Anti-inflammatory & antioxidant 300-1000mg A 3% Vitamin D3 Bone health & immune support 1000-2000 IU A 85% Glutathione Master antioxidant & detox support 250-750mg B 20% Astaxanthin Superior antioxidant & skin protection 4-12mg B 20% Zinc Picolinate Superior immune & healing support 15-30 mg A 95%

Or a different form of the same thing

the comparison people search most

Vitamin C (Ascorbic Acid) vs Vitamin C (Liposomal) absorption 80 against 95 · $10 against $60 a month 95% Vitamin C (Ascorbic Acid) vs Vitamin C (Sodium Ascorbate) absorption 80 against 85 · $10 against $15 a month 85%

All Vitamin C forms ranked by absorption →

Every pair we checked

12 combinations scored by the engine

Vitamin C (Ascorbic Acid) + Copper Bisglycinate High copper may increase vitamin C oxidation Needs attention 70

Vitamin C (Ascorbic Acid) + Caffeine No documented interaction either way No known interaction 70

Vitamin C (Ascorbic Acid) + Creatine Monohydrate No documented interaction either way No known interaction 70

Vitamin C (Ascorbic Acid) + Whey Protein No documented interaction either way No known interaction 70

Vitamin C (Ascorbic Acid) + Turmeric No documented interaction either way No known interaction 70

Vitamin C (Ascorbic Acid) + Lactase Improved calcium absorption when consuming dairy Works better together 82

Vitamin C (Ascorbic Acid) + Bovine Collagen Essential for collagen synthesis and cross-linking Works better together 82

Vitamin C (Ascorbic Acid) + DHA Prevents oxidation of DHA and enhances stability Works better together 82

Vitamin C (Ascorbic Acid) + Vitamin D3 Regenerates oxidized vitamin E Works better together 90

Vitamin C (Ascorbic Acid) + Fish Oil (EPA/DHA) Protects fish oil from oxidation Works better together 90

Vitamin C (Ascorbic Acid) + Calcium Carbonate Essential for calcium absorption and utilization Works better together 94

Vitamin C (Ascorbic Acid) + Iron Sulfate Dramatically enhances iron absorption Works better together 99

Dosage

Divided doses with meals

Daily500-1000 mg

Maintenance200-500 mg

Therapeutic1000-3000 mg

Maximum2000 mg per day (tolerable upper limit)

BowelToleranceVaries 4000-20000 mg (until loose stools)

Upper limit 2000 mg NIH ODS

Before you take it

VeganYes

When to expect it

First Effects24-48 hours for immune benefits

Peak Benefits2-4 weeks for antioxidant status

Deficiency Development4-12 weeks with no intake

Toxicity OnsetRare, mainly digestive upset

How to measure it

$40-80

MarkerPlasma ascorbic acid

Optimal50-114 μmol/L (0.9-2.0 mg/dL)

Deficient below11 μmol/L (0.2 mg/dL)

FrequencyRarely needed unless deficiency suspected

What people actually reported to the FDA

CAERS, 245 reports naming it as the suspect

Most reported effects

Dyspnoea 50

Nausea 22

Hypersensitivity 18

Abdominal pain upper 18

Excluded from the list above: choking (41), dysphagia (19). Those are people struggling with the tablet itself, not with the compound.

Named as the suspect 245 reports of 1,000+ that mention it at all

Serious outcome 79% hospitalisation, emergency room or worse

Other Serious or Important Medical Event167

Visited a Health Care Provider57

Hospitalization53

Reports are voluntary and unverified — they record what someone experienced while taking something, not what the compound caused. Counts skew towards products people take a lot of, and a serious outcome is more likely to be reported than a mild one, so these are not rates. How we filter them →

What actually reaches you

The label counts the carrier, your body does not

Absorption Very high 80 of 100 · best absorbed form of this compound

Delivered daily 600 mg

Cost per 100 mg delivered $0.06 comparative — uses the absorption score, not a measured percentage

Works better with

3 documented

Iron

Dramatically enhances iron absorption

Reduces iron to more absorbable form · level A

Vitamin E

Regenerates oxidized vitamin E

Reduces vitamin E radicals back to active form · level A

Bioflavonoids

Enhances vitamin C activity and absorption

Synergistic antioxidant effects and improved stability · level B

What not to take with Vitamin C (Ascorbic Acid)

2 documented

Copper Excess

High copper may increase vitamin C oxidation

Copper catalyzes vitamin C breakdown · mild significance

Aspirin

May reduce vitamin C levels

Increased urinary excretion · mild significance

Medication interactions

Discuss these with a pharmacist before combining

iron-supplements Beneficial

Enhances iron absorption significantly

What to do: Take together for maximum iron absorption

acetaminophen Minor

May reduce acetaminophen effectiveness

What to do: Space doses apart if concerned

chemotherapy Moderate

May interfere with oxidative cancer treatments

What to do: Discuss with oncologist

Available forms

bioavailability compared

Ranks 7 of 8 among vitamin c forms. Vitamin C (Liposomal) absorbs better — 95%. Compare all forms →

Ascorbic Acid 80

Sodium Ascorbate 85

Liposomal Vitamin C 95

Ester-C (Calcium Ascorbate) 85

Ascorbic Acid: Least expensive, High potency, Well-studied

Sodium Ascorbate: Gentler on stomach, Non-acidic, Better tolerance

Liposomal Vitamin C: Highest absorption, Less GI upset, Sustained release

Ester-C (Calcium Ascorbate): Non-acidic, Contains metabolites, 24hr retention

Food sources

before you supplement

Acerola cherry 1677 mg/100g · 90

Camu camu 2145 mg/100g · 85

Red bell pepper 128 mg/100g · 80

Kiwi fruit 93 mg/100g · 75

Orange 59 mg/100g · 70

Too little

deficiency signs

Fatigue and weakness
Joint and muscle pain
Easy bruising
Poor wound healing
Bleeding gums and dental problems
Frequent infections
Scurvy (severe deficiency): loose teeth, hemorrhages

Too much

toxicity signs

Diarrhea and digestive upset
Nausea and stomach cramps
Kidney stone formation (rare)
Iron overload (in susceptible individuals)
Withdrawal scurvy (rebound effect)
Interference with some medical tests

Who benefits most

smokers

Increased oxidative stress and vitamin C depletion

500-1000 mg daily

athletes

Increased oxidative stress from intense exercise

500-2000 mg daily

elderly

Reduced immune function and slower wound healing

500-1000 mg daily

iron-deficient

Vitamin C dramatically improves iron absorption

100-500 mg with iron-rich meals

stressed-individuals

Chronic stress depletes vitamin C rapidly

500-2000 mg daily

Where to buy it

compare forms first

Look for Vitamin C (Ascorbic Acid) at 500-1000 mg per serving. The form that matters here is Ascorbic Acid.

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How it works

Cofactor for collagen synthesis enzymes
Primary water-soluble antioxidant
Enhances iron absorption by reducing Fe3+ to Fe2+
Regenerates vitamin E and glutathione
Required for carnitine and neurotransmitter synthesis
Supports immune cell function and proliferation

Key findings

what the evidence supports

Reduces cold duration by 8% in general population (Cochrane 2013)
May reduce cold incidence by 50% in athletes (Cochrane 2013)
Essential for collagen synthesis - established biochemistry
Improves iron absorption by 3-4x when taken together (AJCN 2001)

Sources: NIH Examine.com · data reviewed 2026-08-02

Compiled by Denis, who maintains this database and holds no medical qualification — every figure here is sourced or derived, never asserted. How we calculate it →

Common questions

What are the benefits of Vitamin C (Ascorbic Acid)?

Documented effects: Immune system enhancement; Collagen synthesis; Iron absorption enhancement; Antioxidant protection. Reduces duration and severity of cold symptoms by 8-20%

How much Vitamin C (Ascorbic Acid) should you take per day?

The common daily range is 500-1000 mg. By goal — maintenance: 200-500 mg; therapeutic: 1000-3000 mg; maximum: 2000 mg per day (tolerable upper limit); bowelTolerance: Varies 4000-20000 mg (until loose stools).

When is the best time to take Vitamin C (Ascorbic Acid)?

Divided doses with meals. First effects are typically reported within 24-48 hours for immune benefits.

What are the side effects of Vitamin C (Ascorbic Acid)?

At excessive doses: Diarrhea and digestive upset, Nausea and stomach cramps, Kidney stone formation (rare), Iron overload (in susceptible individuals), Withdrawal scurvy (rebound effect). Safety rating at normal doses is 9 out of 10.

What should you not take with Vitamin C (Ascorbic Acid)?

Separate it from Copper Excess, Aspirin by two to four hours. High copper may increase vitamin C oxidation

Does Vitamin C (Ascorbic Acid) interact with medications?

Documented interactions with iron-supplements, acetaminophen, chemotherapy. Discuss these with a pharmacist before combining.

How much Vitamin C (Ascorbic Acid) is too much?

The tolerable upper intake level is 2000 mg per day for adults, per NIH ODS. Above that, the risk of adverse effects rises: Diarrhea and digestive upset, Nausea and stomach cramps, Kidney stone formation (rare).

How do you know if you need Vitamin C (Ascorbic Acid)?

The marker is Plasma ascorbic acid, optimal range 50-114 μmol/L (0.9-2.0 mg/dL). Common deficiency signs: Fatigue and weakness, Joint and muscle pain, Easy bruising, Poor wound healing.

Taken for

59 Immunity

Vitamin D3 · Vitamin C (Ascorbic Acid) · Comprehensive Immune Support Complex

49 Liver & Detox

Turmeric · Vitamin C (Ascorbic Acid) · D-Mannose