Vitamin C Dosage Guide: How Much to Take (Why 1,000 mg Is Overkill)
Adults need 75 mg (women) to 90 mg (men) of vitamin C a day, and smokers 35 mg more. Up to about 200 mg in one dose is fully absorbed; at 500 mg and up the body absorbs less and passes the rest. Our pick, Nature Made Vitamin C 500 mg, gives adults more than enough.
Based on published research, not medical advice. Had kidney stones, have kidney disease or hemochromatosis, or getting cancer treatment? Ask your doctor first.
Ready to buy:
Nature Made Vitamin C 500 mg500 mg in 1 tablet, on USP’s testing list, for $0.08 a day. Why it is our pick.
Costs are brand prices, checked October 19, 2026.
Which amount is right for you?
For most adults, 500 mg a day is plenty. These are the common reasons to choose something else.
Want 1,000 mg a day?
Men’s blood levels topped out at about 1,000 mg a day and women’s at 400 mg (Levine 1996; Levine 2001). Trials that found colds were about 15% less severe used 1,000 mg or more (Hemilä 2023). Nature Made’s 1,000 mg tablet is on USP’s testing list too, for $0.16 a day.
Nature Made Vitamin C 1000 mg
1,000 mg in 1 tablet · USP Verified
Does plain vitamin C upset your stomach?
Try a buffered form. NOW C-1000 Buffered is calcium ascorbate, less acidic than plain vitamin C, for $0.20 a day. Some people find it easier on the stomach; it is not better absorbed. More in vitamin C forms compared.
NOW C-1000 Buffered
1,000 mg in 1 tablet · buffered
Smoke? Add 35 mg.
NIH sets smokers’ daily amount 35 mg higher, because smoking uses up vitamin C. People around secondhand smoke also tend to run low.
How much vitamin C you need, by age
- Men 19 and older: 90 mg a day; upper limit 2,000 mg.
- Women 19 and older: 75 mg a day; upper limit 2,000 mg.
- Pregnant (19+): 85 mg a day; upper limit 2,000 mg.
- Breastfeeding (19+): 120 mg a day; upper limit 2,000 mg.
- Teens 14 to 18: 75 mg (boys), 65 mg (girls) a day; upper limit 1,800 mg.
- Children 9 to 13: 45 mg a day; upper limit 1,200 mg.
- Children 4 to 8: 25 mg a day; upper limit 650 mg.
- Smokers: Add 35 mg a day; upper limit Same.
Source: NIH Office of Dietary Supplements. The upper limit counts food and supplements.
Why more vitamin C stops working
Your gut absorbs vitamin C through a pump that fills up. In NIH studies of volunteers held on a low-vitamin C diet, a 200 mg dose was fully absorbed; at 500 mg and above, the body absorbed less and passed the rest in urine (Levine 1996). Blood levels topped out at about 400 mg a day in women (Levine 2001) and 1,000 mg a day in men. NIH says about 70 to 90% is absorbed at 30 to 180 mg a day, and less than half above 1,000 mg a day. So if you take a big dose, two smaller doses likely absorb more than one.
What the shelf sells: mostly 1,000 mg
We read 900 vitamin C labels in NIH’s label database (26,185 are on the market); 894 listed a dose we could read. 85.6% hold more than the 200 mg your gut fully absorbs in one dose, and 37.2% are exactly 1,000 mg, the most common dose by far. Only 14.4% are 200 mg or less.
- 1,000 mg: 333 labels (37.2%)
- 500 mg: 182 labels (20.4%)
- 250 mg: 73 labels (8.2%)
- 2,000 mg: 26 labels (2.9%)
- 60 mg: 21 labels (2.3%)
A small share, 2.3%, put more than the 2,000 mg upper limit in one serving. If you buy a 1,000 mg tablet, splitting it over the day lets you absorb more of it.
How to take it
- One 500 mg tablet a day covers adults. If you take 1,000 mg, two smaller doses may absorb better than one.
- Take it with food if plain vitamin C upsets your stomach, or switch to a buffered form.
- Stay at or under 2,000 mg a day; more often causes diarrhea (NIH).
Work out your daily vitamin C
Enter the vitamin C on your Supplement Facts panel. Food adds more; most people get their daily amount from food.
Questions people ask
How much vitamin C should I take per day?
Adults need 75 mg (women) to 90 mg (men) a day, and smokers 35 mg more (NIH). Many people get that from food. If you take a supplement, up to about 200 mg in one dose is fully absorbed (Levine 1996), and the adult upper limit is 2,000 mg a day.
Does 1,000 mg do anything a 200 mg dose doesn’t?
A little, for some people. A 200 mg dose was fully absorbed; at 500 mg and above, the body absorbed less and passed the rest (Levine 1996). Men’s blood levels topped out at about 1,000 mg a day, women’s at 400 mg. NIH says less than half is absorbed above 1,000 mg a day.
What has vitamin C been studied for with colds?
A Cochrane review found regular vitamin C did not cut how often most people caught colds, and shortened colds by about 8% in adults and 14% in children. Marathon runners, skiers and soldiers in the cold got half as many colds. Starting it after a cold began had no consistent effect (Hemilä 2013).
Does taking vitamin C with iron help?
In a single meal, vitamin C helps the body absorb iron from plant foods (Lynch 1980). Over a whole diet the effect was much smaller (Cook 2001), and in 440 adults taking iron pills for anemia, adding 200 mg of vitamin C did not help (Li 2020).
Can high-dose vitamin C cause kidney stones?
In men, possibly. Men whose total intake from food and pills was 1,000 mg or more a day had a 41% higher risk (Taylor 2004), and men taking 1,000 mg or more a day from supplements a 19% higher risk (Ferraro 2016). Women showed no link. If you have had stones or have kidney disease, ask your doctor before any vitamin C supplement.
Is liposomal vitamin C worth it?
Usually not. It reached higher blood peaks in studies, but all 10 studies in a 2025 review had industry funding or company authors, none measured how much was lost in urine, and none showed a health benefit (Carr 2025).
Related guides
- Best vitamin C: the products we compared, ranked
- Vitamin C forms compared: plain, buffered, Ester-C and liposomal
- What a day of vitamin C costs
Sources
- NIH Office of Dietary Supplements. Vitamin C fact sheet for health professionals (daily amounts, upper limits, absorption, interactions; updated July 31, 2025).
- Levine M, et al. “Vitamin C pharmacokinetics in healthy volunteers: evidence for a recommended dietary allowance.” Proc Natl Acad Sci USA. 1996. PubMed 8623000
- Levine M, et al. “A new recommended dietary allowance of vitamin C for healthy young women.” Proc Natl Acad Sci USA. 2001. PubMed 11504949
- Hemilä H, Chalker E. “Vitamin C for preventing and treating the common cold.” Cochrane Database Syst Rev. 2013. PubMed 23440782
- Hemilä H, Chalker E. “Vitamin C reduces the severity of common colds: a meta-analysis.” BMC Public Health. 2023. PubMed 38082300
- Lynch SR, Cook JD. “Interaction of vitamin C and iron.” Ann N Y Acad Sci. 1980. PubMed 6940487
- Cook JD, Reddy MB. “Effect of ascorbic acid intake on nonheme-iron absorption from a complete diet.” Am J Clin Nutr. 2001. PubMed 11124756
- Li N, et al. “The Efficacy and Safety of Vitamin C for Iron Supplementation in Adult Patients With Iron Deficiency Anemia: A Randomized Clinical Trial.” JAMA Netw Open. 2020. PubMed 33136134
- Taylor EN, et al. “Dietary factors and the risk of incident kidney stones in men: new insights after 14 years of follow-up.” J Am Soc Nephrol. 2004. PubMed 15579526
- Ferraro PM, et al. “Total, Dietary, and Supplemental Vitamin C Intake and Risk of Incident Kidney Stones.” Am J Kidney Dis. 2016. PubMed 26463139
- Carr AC. “Do Liposomal Vitamin C Formulations Have Improved Bioavailability? A Scoping Review Identifying Future Research Directions.” Basic Clin Pharmacol Toxicol. 2025. PubMed 40506693
- Label count: NIH Dietary Supplement Label Database, vitamin C per serving on 894 labels.