Your body absorbs 70% to 90% of vitamin C when you take 200 mg or less at once, but absorption drops below 50% at doses above 1,000 mg. The sweet spot for a single dose is roughly 200 mg, the point at which your blood levels come close to their maximum without wasting much of what you swallow.
Absorption Rates by Dose
At moderate intakes of 30 to 180 mg, your gut absorbs roughly 70% to 90% of the vitamin C you consume. That means if you eat an orange (about 70 mg of vitamin C), your body takes in nearly all of it. At doses above 1,000 mg, absorption falls below 50%, and whatever does get absorbed but isn’t needed gets filtered out through your urine.
The drop-off isn’t sudden. It’s a curve. A 200 mg dose still absorbs well. A 500 mg dose absorbs a lower percentage, but you still end up with more total vitamin C in your bloodstream than you would from 200 mg. The inefficiency grows with the dose: at 1,250 mg, you’re absorbing less than half, and your kidneys are working to clear the excess. In a landmark pharmacokinetics study from the National Institutes of Health, volunteers showed no urinary excretion of vitamin C until they reached the 100 mg dose. At 500 mg and above, the body began dumping the absorbed excess straight into the urine.
Why Your Body Has a Ceiling
Vitamin C doesn’t passively drift into your bloodstream. It relies on specialized transport proteins called SVCT1, found mainly in the lining of your intestines and kidneys. These transporters actively pull vitamin C molecules across cell membranes using sodium as a co-driver, shuttling two sodium ions for every one vitamin C molecule. This is an energy-dependent, regulated process, not a floodgate.
Because the number of transporters is finite, they can only move so much vitamin C per unit of time. Once those transporters are saturated, additional vitamin C sits in your gut unabsorbed. No matter how much you take orally, your steady-state blood concentration plateaus at about 70 to 80 micromoles per liter. That ceiling is essentially your body’s thermostat for vitamin C, and oral doses alone cannot push past it.
What Happens to the Unabsorbed Portion
Vitamin C that doesn’t get absorbed stays in your intestines, where it draws water into the gut through osmosis. This is why high single doses (typically above 2,000 mg) commonly cause bloating, cramps, and diarrhea. The Tolerable Upper Intake Level for adults is set at 2,000 mg per day specifically because of these gastrointestinal effects.
Even the portion that does get absorbed at high doses doesn’t stick around long. At 1,000 mg daily, researchers found elevated levels of oxalate and urate in urine compared to lower doses. For most people this is harmless, but it’s worth knowing that megadoses mostly end up as expensive urine and potential digestive discomfort.
Splitting Doses Works Better Than One Large Dose
Because your transporters can only handle so much at once, dividing your intake across the day yields more total absorption than taking everything in a single sitting. Two 250 mg doses spaced several hours apart will deliver more usable vitamin C than a single 500 mg dose. Three 200 mg servings spread throughout the day gets you close to the absorption ceiling with minimal waste.
The biological half-life of vitamin C at high plasma levels is relatively short, possibly around 30 minutes, though estimates vary. The practical takeaway: your body clears vitamin C from the blood fairly quickly, so spacing doses at least a few hours apart gives your transporters time to reset and absorb another round efficiently.
Food Sources vs. Supplements
If you’ve wondered whether vitamin C from an orange is absorbed differently than a supplement tablet, the answer is essentially no. Every controlled study comparing synthetic ascorbic acid to food-derived vitamin C in humans has found no meaningful difference in bioavailability at steady state. Some short-term measurements show tiny, transient differences, but they don’t translate to a practical advantage for either form.
That said, food sources naturally deliver vitamin C in smaller, more absorbable amounts alongside fiber, flavonoids, and other nutrients. A single bell pepper has about 130 mg, a cup of strawberries about 90 mg. These portions hit the high-absorption range naturally, which is part of why dietary vitamin C is so efficient.
Do Liposomal Supplements Absorb More?
Liposomal vitamin C, which wraps ascorbic acid in tiny fat-based bubbles, is marketed as a way to bypass the normal absorption limits. There’s some evidence behind this claim. A 2025 scoping review of the available research found that liposomal formulations reached peak blood concentrations 1.2 to 5.4 times higher than standard vitamin C, with total absorption (measured by area under the curve) 1.3 to 7.2 times higher.
The likely reason: liposomal delivery may allow some vitamin C to be absorbed through fat-based pathways in the gut rather than relying entirely on the SVCT1 transporters. However, study designs and formulations varied widely across the research, and these elevated blood levels still don’t necessarily translate into better health outcomes. Whether it’s worth the significantly higher cost depends on your situation. For most people eating a reasonable diet or taking moderate supplements, standard forms are more than adequate.
Practical Takeaways for Dosing
- For maximum efficiency per dose: Keep individual doses at or below 200 mg. You’ll absorb close to 90% of it.
- For higher total intake: Split your daily amount into two or three doses spaced several hours apart rather than taking it all at once.
- For the upper limit of useful oral intake: Blood levels plateau well before 1,000 mg per day. Doses above that produce diminishing returns and more side effects.
- For gut comfort: Stay below 2,000 mg per day total. Above that threshold, diarrhea and cramping become common.
The recommended daily amount for most adults is 75 to 90 mg, a level easily reached through diet alone. If you’re supplementing, you don’t need megadoses. Your body simply isn’t built to use them.