When should I take vitamin C supplements? Tips for optimum absorption.

How much vitamin C can be absorbed? Do we need supplements? When should we take them?
Vitamin C supplements.

In contrast to most mammals, humans cannot synthesis vitamin C. For this reason, vitamin C must be obtained from dietary sources, in order to prevent vitamin C deficiency (5).

Vegetables and fruits are the only foods that contain adequate amounts of vitamin C.

To see the whole list of the most common foods that are rich in vitamin C, click here.

As people worry about the flu or the common cold, they tend to take vitamin C supplements, in order to boost the immune system. Moreover, there are more effective cold and flu treatments, without the use of supplements.

But…if someone decides to take vitamin C supplements, at least follow these tricks, in order to maximize the effects of supplementation.

How much vitamin C can be absorbed at a time?

When consuming vitamin C, the body produces tissue and plasma concentrations. The vitamin C absorption depends on the dose (6).

  • moderate intakes of 30–180 mg/day. The vitamin C is absorbed to 70% – 90%.
  • at doses above 1000 mg/day, the vitamin C absorption drops to less than 50%.

The more isn’t always better…

Excess vitamin C is excreted in the urine.

Studies have shown that even relatively high doses of vitamin C won’t elevate the vitamin C plasma concentrations much more than normal (6).

For instance,

  • 200 – 300 mg/day vitamin C consumed by food, produced plasma vitamin C concentrations of 70 micromol/L,
  • 1250 mg/day produced plasma vitamin C concentrations of 135 micromol/L, while
  • 18000 mg/day can produce peak plasma concentrations no more than 220 micromol/L.

Excess vitamin C is excreted in the urine.

The recommended daily intake of vitamin C is only 90 mg. It’s really easy to eat 90 mg of vitamin C on a whole food plant-based diet.

One dose or more during day?

It is preferred to split up your doses throughout the day, rather than taking just a big dose once a day.

This way you can improve absorption, limiting excreting of the vitamin C in urine and reduce chances for side effects, like nausea.

Another advantage is that you’ll have high plasma concentrations of vitamin C all day.

How much vitamin C do we need?

The total body content of vitamin C ranges from 300 mg to about 2000 mg.

300 mg is the down limit, at near scurvy.

High levels of vitamin C are maintained in cells and tissues, and are highest in white blood cells, eyes, adrenal glands, pituitary gland, and brain.

Lower levels of vitamin C are found in plasma, red blood cells, and saliva (6)

The recommended daily vitamin C intake is about 90 mg. Pregnant women and smokers require additional vitamin C intake. More details here.

When should I take vitamin C? Is morning the best time?

What water-soluble vitamin means?

Vitamin C is a water-soluble vitamin. That means that it dissolves in water so your body can use it. Most importantly, water-soluble vitamins don’t store in the body in high concentrations.

Therefore, it’s difficult to obtain vitamin toxicity. Contrary, it is necessary to take water-soluble vitamins, like vitamin C, daily.

Remember, don’t take a high dose, such as 1000 mg of vitamin C, as it’s a waste of money. Our body will absorb the amount of vitamin C it needs and the rest will be extracted through urine.

Best time to take water-soluble vitamin C

Vitamin C can be taken on either an empty or full stomach.

As vitamin C is a water-soluble vitamin it can easily be absorbed on an empty stomach. That may be a problem for some people though, as can cause upset digestion and even diarrhea.

As a rule of thumb, it’s generally better to take vitamin C supplements with a meal, in order to avoid digestion problems.

Consider taking the biggest dose of vitamin C supplement during the breakfast time.

Rember, there is no need to take a higher dose than 200 – 300 mg daily and for better results, you should split this dose in 2 – 4 times during the day.

Buy vitamin C capsules of 250 mg.
You can also cut them down to 2 - 3 parts.

Try to take the biggest amount of vitamin C in the morning.

You’ll boost your immune system and help your body to perform properly during the day. For instance, vitamin C helps your skin to stay young, fighting free radicals and preventing damage from sunlight.

Also, vitamin C is beneficial to the human eye and helps to prevent eye-related diseases, like macular degeneration, as it’s a strong antioxidant (7).

Vitamin C is very important for protecting your eyesight.

It’s always better to have provided the body with adequate vitamin C before skin and eye exposure to the damaging sunlight.

Seems like most people are a person of habit, so establishing a daily routine of taking your vitamin C at the same time every day will help you stay consistent.

What enhances vitamin C absorption?

Supplemental vitamin C typically takes about two hours to reach maximal plasma levels following ingestion. What factors can affect the bioabsorption of vitamin C though?

The most important factor is the levels of vitamin C plasma concentrations.

To put it simply, if the body has reached the maximum level of vitamin C that can metabolize, it won’t absorb efficiently any excess amount of vitamin C.

Scientists have shown that doses of 500 mg vitamin C have reduced intestinal bioavailability (2). Saturation levels of vitamin C are much less than 500 mg. That’s the reason we recommend many low doses throughout the day rather than a big one.

Vitamin C is absorbed more efficiently through diet.

In some research, citrus fruit extract has used in comparison with vitamin C supplements. Citrus juice delayed the maximal plasma levels of vitamin C by one hour and provided a 35% increase in vitamin C bioavailability (2).

Also, the citrus fruit extract increased the vitamin C excretion from urines, when the body was saturated with vitamin C. That didn’t happen when volunteers’ body needed vitamin C (2).

Don’t worry about what foods or supplements provide better vitamin C absorption. Research has suggested that ascorbic acid ingested as cooked broccoli, orange juice or fruit, or in synthetic form seems to be equally bioavailable (8).

Even if raw broccoli has slightly lower relative bioavailability of ascorbic acid than the cooked, it’s unlikely to be of practical importance (8).

Just mix things up and 
eat lots of fruits and vegetables rich in vitamin C. 

You can find the most common foods rich in vitamin C, here.

Optimal vitamin C intake: Supplements or food?

Synthetic and food-derived vitamin C is equally bioavailable in humans (2).

A recent study has shown exactly that. Vitamin C from food (kiwi fruit) is comparable to synthetic (5).

What is the preferred vitamin C intake though? From food or supplements?

Probably vitamin C derived from food is preferable.

The reason is that food provides many other macronutrients, micronutrients, and phytochemicals, which cooperatively provide additional health benefits (2).

Phytochemicals like flavonoids may affect the bioavailability of food-derived vitamin C. Flavonoids act as antioxidants, effectively fighting free radicals (5).

Food flavonoids can increase vitamin C bioavailability (5).

Numerous epidemiological studies have indicated that higher intakes of fruit and vegetables, foods rich in vitamin C, and other phytochemicals, are associated with decreased incidence of stroke, coronary heart disease, and cancers at various sites (2).

Can you absorb vitamin C through the skin?

If you worry about your skin protection or skin healing, you maybe have noticed creams containing vitamin C. Are they effective though?

That highly depends on the saturation of vitamin C in your body.

If you experience vitamin C deficiency, vitamin C creams can help you.

The bioavailability of vitamin C in the skin is inadequate when it has been administered orally. That’s because the absorption of vitamin C in the gut is limited. Only a percentage of the vitamin C supplementation is absorbed, even in high oral dosage.

Consequently, the use of topical vitamin C is preferred for skin therapies (3).

Vitamin C creams are useless if you follow a healthful nutrition.

In contrast, a study showed that there is no need for topical application of vitamin C if the health of the patient is already optimal.

In this case, there is no absorption of vitamin C. Scientists admired the importance of nutrition.

They said that healthful nutrition can be more effective than topical application (4).

How can I increase my vitamin C fast?

Just remember…Vitamin C is a water-soluble vitamin. The body can’t store, or synthesis it. As an aftermath, we have to consume it daily through food or supplements.

Prefer vitamin C intake from food. Vegetables and fruits are foods that are a good source of vitamin C.

Is 1000mg of Vitamin C safe?

If you decide that you need an extra boost of vitamin C, you can take supplements. Ask your doctor for the dose you need.

1000 mg of vitamin C is safe dose.

Prefer to consume vitamin C supplements throughout the day, from taking just one pill in the morning.


  1. NCBI – PMC: Vitamins and Sleep: An Exploratory Study
  2. NCBI – PMC: Synthetic or Food-Derived Vitamin C—Are They Equally Bioavailable?
  3. NCBI – PMC: Vitamin C in dermatology
  4. NCBI – PMC: The Roles of Vitamin C in Skin Health
  5. NCBI – PMC: A Randomised Cross-Over Pharmacokinetic Bioavailability Study of Synthetic versus Kiwifruit-Derived Vitamin C
  6. National Institutes of Health – Vitamin C
  7. NCBI – PMC: Nutrients for Prevention of Macular Degeneration and Eye-Related Diseases
  8. NCBI – Pubmeb.gov: The bioavailability to humans of ascorbic acid from oranges, orange juice, and cooked broccoli is similar to that of synthetic ascorbic acid.