Supplement Comparison
All vitamin C supplements are not the same. Five different forms are sold, three different absorption rates apply, and the price per effective dose can swing 5×. This page ranks 10 products by what actually gets into your blood.
Last updated: July 28, 2026 · Sources: NIH ODS, Examine.com, peer-reviewed PubMed
Best absorption
Liposomal Vitamin C
Plasma AUC 1.4× plain ascorbic acid (Davis 2016). Premium price.
Best budget
NOW Foods C-1000
Plain ascorbic acid. Lowest per-mg cost. Used in most clinical trials.
Best for sensitive stomach
Buffered Ascorbic Acid
Sodium ascorbate (pH-neutral). Less GI upset at doses >1000mg.
Compare 14 popular vitamin C products on dose, form, bioavailability score, and Thailand availability. Prices are price-per-month at the daily dose; per-milligram cost follows the math at the top of each card.
| Brand / Product | Form | Dose | Bioavail | Price (date) | TH | Vegan |
|---|---|---|---|---|---|---|
| Ascorbic Acid | 1000mg | 3/5 | $9.99 2026-07-20 | ✓ | ✓ | |
| Buffered Sodium Ascorbate | 1000mg | 4/5 | $24.50 2026-07-20 | — | ✓ | |
| Liposomal | 1000mg | 5/5 | $39.95 2026-07-20 | — | ✓ | |
| Ester-C | 1000mg | 3/5 | $19.95 2026-07-20 | — | ✓ | |
| Ascorbic Acid | 1000mg | 3/5 | $16.50 2026-07-20 | ✓ | ✓ | |
| Ester-C | 1000mg | 3/5 | $22.95 2026-07-20 | — | ✓ | |
| Calcium Ascorbate | 1000mg | 3/5 | $28.00 2026-07-20 | — | ✓ | |
| Ascorbic Acid | 1000mg | 3/5 | $17.95 2026-07-20 | — | ✓ | |
| Ascorbic Acid | 1000mg | 3/5 | $18.00 2026-07-20 | — | ✓ | |
| Ascorbic Acid | 1000mg | 3/5 | $11.99 2026-07-20 | — | ✓ | |
| Calcium Ascorbate | 1000mg | 2/5 | $18.50 2026-07-20 | — | ✓ | |
| Ascorbic Acid | 500mg | 3/5 | $9.95 2026-07-20 | — | ✓ | |
| Ascorbic Acid | 500mg | 3/5 | $14.95 2026-07-20 | ✓ | ✓ | |
| Liposomal | 1000mg | 5/5 | $32.95 2026-07-20 | — | ✓ |
Bioavailability 1/5 = weak, 5/5 = strongest absorption. Prices marked "[price unavailable]" reflect our rule: no published price without a verifiable URL+date.
Bioavailability: 3/5
The form used in essentially every vitamin C clinical trial, including the Linus Pauling Institute saturation studies. Oral absorption saturates at roughly 200 mg per dose — taking more than that largely goes unused. Cheap to make, found in every supermarket. May upset the stomach above 1 g per dose.
Best for: daily users on a budget, people who split doses across the day, anyone taking ≤500 mg at a time.
Bioavailability: 4/5
Ascorbic acid bound to a mineral (sodium or calcium) — pH-neutral. Easier on the stomach at high doses because the molecule no longer carries the acidic proton. Same plasma vitamin C levels as plain acid at equal dose. A real win for people who get nausea or acid reflux from ascorbic acid.
Best for: sensitive stomachs, anyone taking 1 g+ per day, people prone to kidney stones.
Bioavailability: 5/5
Ascorbic acid encapsulated in phospholipid (lecithin) bubbles — the same kind used in IV vitamin C in clinical trials. Peer-reviewed evidence (Davis 2016, Nutrients) shows plasma C is ~1.4× higher AUC than plain ascorbic acid. Significantly more expensive per gram. Worth it for clinical dosing (5+ g/day) or anyone with absorption issues.
Best for: high-dose protocols, malabsorption, anyone whose stomach cannot tolerate 5+ g of plain acid.
Bioavailability: 3/5
Patented form (InterPlexus): calcium ascorbate plus small amounts of vitamin C metabolites (dehydroascorbate, calcium threonate). Marketed for "24-hour retention" — the claim is plasma C stays elevated longer vs plain acid. Examine.com rates the evidence as mixed: arguably slightly better cellular uptake, but no clear-cut advantage for most healthy adults.
Best for: people who want a buffered form and like the "metabolite retention" angle.
Bonus discussion
IV vitamin C bypasses intestinal saturation entirely. Plasma levels reach 5–10× what oral dosing can achieve. This page does NOT compare IV because it is a clinical intervention. If you have cancer treatment fatigue or serious deficiency, talk to your doctor — that is the appropriate context for IV dosing.
Set by the US Institute of Medicine (IOM 2000) and mirrored by most national authorities. Tolerable upper limit per dose that triggers diarrhea is roughly 2 g — split doses help.
| Group | RDA (mg/day) | UL (mg/day) |
|---|---|---|
| Adult men | 90 | 2,000 |
| Adult women | 75 | 2,000 |
| Smokers (any sex) | +35 over baseline | 2,000 |
| Pregnancy | 85 | 2,000 |
| Lactation | 120 | 2,000 |
Source: NIH Office of Dietary Supplements (ods.od.nih.gov) · UL = tolerable upper intake level (no adverse effects in healthy adults).
Best budget
Plain ascorbic acid from a 55-year-old manufacturer at the lowest per-mg cost — typically the form used in clinical trials.
Best absorption
The original liposomal brand, longest track record, peer-reviewed evidence for higher plasma AUC vs plain ascorbic acid.
Best for sensitive stomach
Practitioner-grade, hypoallergenic sodium ascorbate (pH-neutral) for users who get GI upset from plain ascorbic acid.
Best Thailand-available
Readily available at Chemist Warehouse / Watsons / Boots Thailand. Plain ascorbic acid — but locally sourced.
Best for flexible dosing / athletes
Bulk crystalline powder — fan control your dose (0.5g, 1g, 5g+). Cheapest per gram.
Best vegan & eco
Ascorbic acid + rose hip bioflavonoids. Hypoallergenic, certified vegan.
These 10 brands are featured on every vitfacts.com comparison page. We track them for ingredient transparency, third-party testing, and Thailand availability.
Since 1969
One of the most globally recognised Australian brands, dominating the market with comprehensive multivitamins and targeted wellness blends.
Since 1932
A heritage naturopathic brand spanning over 90 years, known for rigorous ingredient sourcing and massive pharmacy presence throughout the Asia-Pacific region.
Since 1993
A premium, practitioner-only brand (owned by Blackmores) offering highly concentrated, clinical-strength formulas that are frequently recommended by healthcare professionals.
Since 1986
A high-quality pharmacy brand heavily focused on evidence-based ingredients, widely known for its "Inner Health" probiotic range and highly absorbable magnesium powders.
Since 1980s
Born in Australia, this brand formulates therapeutic herbal and nutritional supplements with a strict focus on purity, offering many vegan-friendly options.
Since 1970s
One of Australia's longest-running and most accessible vitamin brands, providing a massive, budget-friendly range found in most major supermarkets and pharmacies.
Since Thailand
A dominant local brand in Thai retail pharmacies (such as Watsons and Boots), highly popular for its acerola cherry, collagen, and beauty-focused supplements.
Since 1982
A leading pharmaceutical-grade supplement brand in Southeast Asia, widely trusted by Thai consumers for its fish oil and targeted clinical nutrition products.
A fast-growing biotech and nutraceutical brand in Thailand, making a name for itself with premium probiotics and anti-aging wellness supplements.
Since 1984
While based in the US, Thorne is heavily imported and highly sought after by functional medicine practitioners globally—including in both Australia and Thailand. It is considered a gold standard due to its strict four-round testing protocol and complete absence of unnecessary fillers or binders.
Why these 10? See the VitFacts editorial policy page (forthcoming) for the criteria — minimum 10 years of documented safety record, public certificate-of-analysis policy, and verifiable Thailand distribution.
