how long for vitamin d to work

How Long Does It Take For Vitamin D To Work?

In this article you’ll learn the answer to two questions:

  • ​How long does it take for supplementation to raise your vitamin D blood levels?
  • ​How long does it take for you to feel the effects of vitamin D?

Did you notice the subtle difference?

Raising your vitamin D levels is important, but if you suffer from an autoimmune disorder there’s so much more that vitamin D can do ​for you.

For example, Dr. Coimbra, in Brazil, and many other Doctors, worldwide, are using high-dose vitamin D therapy to stop the progression of serious autoimmune disorders, like multiple sclerosis. 

That’s why, in the second half of this article, you’ll learn how much time vitamin D takes to help you feel relief.


And, In case you're wondering how vitamin D can be used to put such serious diseases into remission (and what steps must be taken to stay safe while doing it) be sure to take a look at my book How Not ot To Diw With True High-Dose Vitamin D Therapy.

Here are some of the glowing Amazon reviews:

​Erick Hernandez

​October 15, 2019

​The BEST vitamin D book out there

Honestly, after getting diagnosed with MS and not wanting traditional pharmaceutical treatment I did a solid amount of research into natural remedies... Of all the books I purchased on Amazon in reference to treating MS with vitamin D, this book has been my favorite! It's very informative and an easy read! I recommend it for anyone looking into vitamin D treatment and especially those who are following the Coimbra protocol!

Gabriel F. MD

July 27, 2018

​Amazing Book !!!

The book explains, like no other, the treatment with high doses of vitamin D3. To understand in depth the Coimbra's protocol, the author analyzes the biological and pathological bases to establish the foundation of the treatment. It does not leave any concept without understanding. The author of this book reveals an enormous capacity and enormous humility and intelligence.
Thank you very much, Tiago

​John K Marchi

​October 15, 2019

Obviously a very knowledgeable writer

This is the fourth book I have read on the topic of High Dose Vitamin D3. Without a doubt the best read so far. The author has gone to great lengths to clearly lay out all of the pros and cons of the topic. Of special importance is the addition of Vitamin K2. That has been very well explained. An easy read, even for a layman like me!

​Just click "Look inside" and you can read the initial chapters for free​.​ No sign-up is required. And, if you don't like the book, Amazon as an awesome, no-questions-asked return policy.

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​How long does it take for supplementation to raise your vitamin D blood levels?

Most people take vitamin D with the goal of correcting a deficiency.

How can long does this take?

After you begin supplementing with vitamin D, it may take up to a week for your blood levels to rise significantly. ​

How much they’ll raise, however, will be dependent on at least 2 factors:

  • 1
    ​Your starting vitamin D blood level.
  • 2
    ​Your dosage – how much vitamin D you take and how frequently you take it.

1. Your starting vitamin D blood level

If you are severely deficient when you begin your treatment it may take you longer to recover. (1)

Let’s imagine that having a vitamin D deficiency is like being dehydrated and that vitamin D is our water.

How much water will it take to rehydrate your body?

The higher your state of dehydration the greater the amount of fluids you’ll need. This seems like common sense, and it is.

The second factor influencing your recovery is your dosage.

2. Your dosage – how much vitamin D you take and how frequently you take it.

After analyzing the results from 25 studies, a group of researchers produced this helpful graphic: (2)

change in serum vitamin D levels

As expected, the higher the daily vitamin D intake, the greater the gains were.

10,000 IU of vitamin D per day is often considered the highest dose a person can safely take every day without having to worry about adverse effects, and, as expected, it produced the highest changes in vitamin D levels when compared with the lower dosages.

However, as you can verify for yourself, by paying close attention to the varying positions of the blue dots, this growth is far from linear.

For example, some people taking 4,000 IU of vitamin D saw an increase of 20 nmol/mL at the end of the study, while others saw their levels increase by 120 nmol/mL.

Why this variation?

Let’s go back to the water-vitamin D comparison.

If you want to stay hydrated while exercising, you’ll need to drink a greater amount of water than a person who spends his day watching TV.

Moreover, if you had eaten a lot of salt, you’d need even more water to keep your body hydrated.

Similarly, just like exercising depletes your water reserves, stressful situations deplete your vitamin D reserves.

And, just like eating a lot of salt increases your body’s demand for water, certain habits, like smoking, will also increase your need for higher doses of vitamin D because of the way they hinder vitamin D metabolism.

The same is true for several common medications, like cortisone and its derivates or anti-acids. These drugs make it more difficult for your organism to process vitamin D.

On top of that, if your body doesn’t have access to the necessary co-factors that it requires to process vitamin D – like magnesium and vitamin B2 – it won’t be able to fully utilize the vitamin D you are ingesting.

For all these reasons, it’s easy to see how one person may take 4,000 IU every day, for 2 months, and see his vitamin D levels raise to optimum levels, while another might take the exact same dose and see no discernible progress – even if they both started with the same baseline blood level of vitamin D.

In the same way, by paying close attention to these factors you can improve your chances of recovering faster.

If it can take just ​​​One week to see an improvement in the blood levels, why do Doctors wait ​Eight or more weeks before repeating the lab tests?

To correct a vitamin D deficiency, Doctors can prescribe either a daily or a weekly dose of vitamin D.

Daily doses can differ a lot depending on your baseline levels, age, and health status.

Weekly doses tend to be larger, such as 50,000 IU or higher.

And, even though it may take you just one week to begin recovering, your Doctor will usually wait for 2 to 3 months before retesting your blood levels and adjusting your dosage.


Suppose you took 10,000 IU of vitamin D 7 days ago and today your Doctor decided to check your levels.

What would he learn?

He’d be able to see the effect that the first doses of vitamin D had on your blood levels.

Now, if you had taken just a single dose of vitamin D 7 days ago, this would be fine. But you kept taking 10,000 IU every day.

You took this dose 6 days ago, 5 days ago, and every single day since.

Therefore, what’s the point of measuring your blood levels today? After all, tomorrow they could be higher, and even higher 2 days from now.


Because of the compounding effect of all the other capsules of vitamin D that you kept taking in the second, third and following days since you began supplementing 7 days ago.

Not to mention that all those factors mentioned earlier, such as your stress levels, the drugs you take, and even your own metabolism, can influence the exact time when that first dose will most impact your levels.

When can you trust your blood levels, then?

Your blood levels won’t keep increasing forever but, since you are supplementing every day, it’ll take some time for them to stabilize.

By waiting 2 to 3 months, you’ll give your body enough time to reach and to remain at that peak level.

At this point in time, your Doctor can look at your blood levels and be sure that, as long as you keep taking 10,000 IU per day, your levels shouldn’t change significantly.

Now he can make a much more thoughtful decision.

If your vitamin D levels are still lower than they should, your Doctor will increase your dosage by a sensible amount and wait another 2 or 3 more months before checking them again.

Likewise, if your levels are too high, he’ll lower your dosage and, once again, wait.

But, if your numbers are right on target, he’ll ask you to maintain your dosage. However, he’ll most likely still check your blood again in 2 to 3 months, just to make sure everything goes according to his expectations.

What if you are still symptomatic even after reaching a vitamin D level that your Doctor considers optimal?

That leads us to the second question we asked at the beginning of this article.

After all, getting your blood levels to raise is one thing, actually feeling better is another.

time hourglass

​How long does it take for you to feel the effects of vitamin D?

Each individual reacts differently to supplements.

In the case of vitamin D, how long it’ll take for it to work in your case is dependent on 3 factors. Two of them are already familiar to you, as we have just covered them:

  • 1
    ​Your starting vitamin D blood level.
  • 2
    ​Your dosage – how much vitamin D you take and how frequently you take it.

If you want to feel the effects of vitamin D, though, you need to take into account a third essential factor:

  • 3
    ​Your body’s ability to utilize the vitamin D you are supplementing it.

In practical terms, this means that you can have a high-level of circulating vitamin D but your body may still be unable to activate it and have it reach the places where it is most needed.

Take my wife Miriam, for example. Even though at one point she was taking 40,000 IU of vitamin D every day, she wasn’t feeling any significant improvement in her joint pain.

Her vitamin D blood levels were well above 100 ng/mL (250 nmol/l) and it still seemed vitamin D was worthless at helping her with her autoimmune disorder.

It took her a much higher dosage to finally find relief.

You can learn more about Miriam’s story here.

What was the problem?

Factor number 3.

As it often happens with those of us suffering from autoimmune disorders, Miriam’s body is resistant to vitamin D.

Or, in other words, it seems that during the long chain of events all the way from “Miriam takes a vitamin D capsule” to “vitamin D gets processed, activated and used to take control over Miriam’s immune system,” there was a lot of vitamin D going to waste.

There should have been more than enough vitamin D circulating in Miriam’s blood, but her immune cells weren’t reacting to it.

What’s the point of measuring your vitamin D levels, then?

Checking your levels will tell you how much at risk you are from suffering the side-effects of a vitamin D overdose.

You see, as your levels rise beyond 100 ng/mL, so do your chances of toxicity in the form of hypercalcemia and hypercalciuria.

That’s due to the way vitamin D increases your calcium absorption from food.

In a nutshell, knowing your vitamin D blood levels is useful because they’ll let you know how careful you need to go about your calcium intake.

Unfortunately, they’re pretty much useless at telling you how long it’ll still take you to tame your immune system.

For example, certain patients from Doctor Coimbra need to increase their vitamin D levels to the thousands of ng/mL before they’ll feel relief – as reported by Ana Claudia Domene, herself a patient of Dr. Coimbra, in her book.

These might be the outliers, but still, they illustrate the point well:

If you have an autoimmune disorder and are taking vitamin D in the hopes of stopping its progression, checking your vitamin D levels shouldn’t be your primary focus.

You need a better marker for vitamin D efficiency than 25-hydroxyvitamin-D itself.

​​What is 25-hydroxyvitamin-D?

When you take a gelatin capsule of vitamin D3, you are ingesting a chemical known as cholecalciferol.

Some of this cholecalciferol will be absorbed and end up in your bloodstream.

Over there, it’ll travel through your organs, including your liver and your kidneys, where it’ll be processed and transformed.

During these transformations, your body will “digest”, or metabolize, the vitamin D you took into several different chemicals.

These chemicals are known as vitamin D metabolites because they’re the result of vitamin D metabolization.

One of these chemicals is 25-hydroxyvitamin-D.

Therefore, when a Doctor, or a researcher, wants to know if your vitamin D3 (cholecalciferol) supplementation is being effective or not at raising your levels, he’ll draw some blood from you and measure your 25-hydroxyvitamin-D levels.

If 25-hydroxyvitamin-D levels are raising this means your body is using up the cholecalciferol you are taking, metabolizing it not only in 25-hydroxyvitamin-D but it the other many vitamin D metabolites.

25(OH)D is the same as 25-hydroxyvitamin-D. They’re synonymous. 25(OH)D is simply the abbreviated form.

Other less common synonymous include calcidiol and the 25-hydroxycholecalciferol.

​That’s exactly why Dr. Coimbra pays so much attention to your PTH levels.

After all, influencing your PTH levels is the last measurable step in the chain of events promoted by vitamin D.

In other words, if your PTH is coming down, the high-dose protocol is working.

This is true, of course, as long as there are no other factors responsible for your low PTH levels.

Such factors would include a malfunctioning parathyroid gland or high calcium blood levels.

But, if you are following a low-calcium diet and your calcium levels are well within the normal range and your parathyroid gland is healthy, a drop in PTH can be traced back to the high-dose vitamin D you are taking.

In Miriam’s case, for example, even though 40,000 IU of vitamin raise her levels to more than 100 ng/mL, her PTH was still midrange.

She had a large quantity of circulating vitamin D but not a sufficient amount being activated and deployed to tame her immune system or suppress her parathyroid hormone production.

With this in mind:

​​how long does high-dose vitamin d take to work?

It depends on how fast you can find the vitamin D dose that can lower your PTH levels.

Once you find it, it should take around 1 to 2 weeks for this dose to reach its peak circulating value and you’ll then feel the maximum relief allowed by this dosage.

However, since the starting dosages will tend to be much lower, and it may take several readjustments to find the best dosage for you, it may take you 6 or more months to truly feel the effect of the right dose of vitamin D over your autoimmune disorder.

How can you find the right dosage for you?

This dosage is found through trial and error, over the course of many months.

Waiting increases both your certainty and your safety.

Just bear in mind that you need to be sure your PTH levels aren’t below the minimum value allowed by the laboratory reference range.

PTH is essential for life, so you want to keep it at the lowest level allowed by the lab range, but no more than that – unless your Doctor is very well familiarized with the intricacies of the Coimbra Protocol and directs you to do so. Such a thing could happen if you were still symptomatic even after reaching the minimum PTH value allowed by the reference range.

The next step for getting relief

The whole process of balancing your calcium intake, correctly interpreting all the blood tests and adjusting your vitamin D dosage, not to mention the need to follow all the safety guidelines, take the essential co-factors, and knowing how to deal with the sudden flair-ups can be overwhelming.

I and my wife have an idea of how that feels, as we’ve gone through that same process ourselves.

For this reason, if you are feeling lost be sure to check our book on how not to die with true high-dose vitamin D therapy where you’ll find a step-by-step guide teaching everything you need to know on safe high-dose vitamin D and vitamin K2 supplementation.

​How did researches came up with the one week average?

​Knowing what happens to a chemical compound after it gets inside of your body is very important.

That’s the goal of fields such as pharmacokinetics and pharmacodynamics.

But, if every person is different, how can scientists ever reach a conclusion?

By studying a drug’s effect in a large sample of people​, scientists can estimate how much it’ll take for an average person to react to it.

For example, in 2012 a group of researchers published a paper on the effects of a single dose of 70,000 IU of vitamin D in 61 women, 27 of whom were pregnant. (​3)

How long did it take for 70,000 IU to raise these women vitamin D blood levels?

See if you can tell:

vitamin D changes over time 1

The graphic you are looking at, labeled “A” refers to the results obtained by measuring the levels of the 37 non-pregnant women.

The circles represent the distribution of the results.

serum vitamin d changes labels

​As you can see by looking at day-0, each woman begun the study with widely different 25-hydroxyvitamin-D levels.

For this reason, and because each person’s metabolism is unique, the circles never converge to a single point.

However, by crunching the numbers, researchers came up with a line representing the way their blood levels changed over the course of a 70-day period.

Their conclusion was that, for the non-pregnant women, the 25-hydroxyvitamin-D levels were “an average of 19 nmol/L higher than baseline (…) during the first month after supplementation.”

Or, in other words, if a non-pregnant woman were to take 70,000 IU of vitamin D right now, she would be likely to see an increase of about 19 points in her 25-hydroxyvitamin-D blood levels during the first 30 days.

This, of course, is an average.

Some women just got a 12 nmol/L increase, while others saw a 25 nmol/L raise.

Most interesting is how long it took for their levels to rise.

Just by looking at the graph, you can see a steep increase during the first 4 days with the peak level being reached around the seventh day – the first week.

This can also be observed in the group of 27 pregnant women:

vitamin D changes over time 2

Even though the peak 25-hydroxyvitamin-D levels were observed around the 21st day, the steep increase is seen during the first 7 days.

How do these results compare with the outcomes obtained by similar studies?

This study was performed in South Asian women, nevertheless, in the researchers own words: “The occurrence of the maximal mean [25(OH)D] in the first month was consistent with previous studies of single-dose vitamin D3 (1.25 to 15 mg) administered to non-pregnant adults in North America, Europe and Australia.” (​4)

However, bear in mind that these values were for a single administration of vitamin D, albeit a large dose. That’s why you can expect your blood levels to be higher after a single week of supplementation – even if you have just supplement one single time – provided, of course, that the dose you have been prescribed was significant enough.

Moreover, if these women had continued to take vitamin D every single day after their initial dose, the line would take longer than a week to stabilize – hence a Doctor’s desire to wait 2 to 3 months before retesting your levels.

Tiago Henriques

With more than 10 years of experience as a Public Speaker, Tiago Henriques has done hundreds of public talks. He was born in 1987, in Portugal, and is the Author of 3 books — and counting — and the creator and editor of the Portuguese Science Project, "Ciência Desenhada," where complicated science is explained in a simple way, using whiteboard animation techniques. Tiago developed his own practical and down-to-earth teaching method inspired by his experiences with the Portuguese Deaf Community and their use of highly visual, descriptive and easy-to-understand language.

  • d says:

    this is not helpful, because this doesnt explain the relation between “Blood level – period of taking vitaminD”.

    • HI D, I’m sorry you didn’t found the article helpful. As you can see from the available graphs, the relationship between “blood level” and “period of taking vitamin D” is variable as it depends on factors that differ from person to person such as the absorption rate. Most Doctors will wait between 2 to 6 months after you begin supplementing to test your blood levels so that they can get a stable reading of your levels. However, and this is great news, the time it takes from vitamin D to have an impact on your system is actually much lower as the article explains.

  • jackie says:

    how long does it take if your Vitiamin -D level was 16ng ,and im taking 50.000 unit a week to build up

    • Hi Jackie,

      Unfortunately there isn’t a clear answer as it will depend on your absorption rate, among other factors. However, I’d expect them to build up fast, especially since your starting level is very low. 50,000 IU per week is the usual dosage prescribed by Doctors as it is very safe. Usually, you’ll get your level checked after 2 months. If they are still below optimal, but significantly better, you’ll most likely remain on that dosage for another 2 months. If they have failed to improve (due to malabsortion or other unknown factor) and if the remaining blood tests are fine, your Doctor will up the dosage.

      Either way don’t worry too much about it, as you are on the right path to improve your levels.

      Hope this helps

  • Connie Teeters says:

    Does it matter what kind/type you are taking? I’ve been taking K2 D3 in liquid form

  • Zadok says:

    Hello Tiago,

    Once you have found the ‘right dose’ of vitamin D based on self-perception and blood/urine test, do you have to stay on that dose for the rest of your life? Will vitamin D eventually ‘cure’ the problem?

    • Hi Zadok, based on the reports on the Brazilian Facebook groups, the dosage may be adjusted over time. This is specially true when one manages to keep his stress levels under control. The higher your stress levels the greater the vitamin D necessary to keep the immune system under check. In fact, high stress is one of the factors undermining the action of vitamin D.

      Also, high-dose vitamin D doesn’t seem to be the only way to get an autoimmune disorder under control. Several dietary approaches focusing on anti-inflammatory, and microbiome friendly, food seem to be successful to. This is true even when they don’t include high-dose vitamin D supplementation. Therefore, it stands to reason that combining such approaches with the high-dose protocol would make you need less vitamin D to achieve the same goal.

      So I wouldn’t be surprised if even a modest attempt at improving one’s diet, coupled with an improvement to one’s strategy to deal with stress, would have a significant impact on how much vitamin D is needed overtime.

      • Zadok says:

        Thank you. That makes sense. From your knowledge, is it possible to have normal blood calcium levels and yet still develop kidney problems or even high calcium in the urine as a result of high-dose vitamin D?

        • Yes. That’s why you need to test for both. High blood calcium occurs when your kidneys are unable to filter out the excess calcium. This may be an indication that you are taking too much vitamin D or too little co-factors, that your bones are leeching out too much calcium, that you are ingesting too much calcium, or that your kidneys are overwhelmed or failing.

          That’s why there’s usually a battery of tests done to assure that all bases are covered. So, if your Doctor only tests for blood calcium he may think that everything is fine, when in fact your kidneys may have been overwhelmed for quite some time.

          Kidney problems should not occur when you are being followed by a knowledgeable Doctor though, as you’ll be properly vetted before starting the therapy (i.e. that your kidneys can handle it) and your dosage will be adapted to your body’s response to vitamin D.

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