Can you take high doses of vitamin D while pregnant?

Can You Take High Doses Of Vitamin D While Pregnant?

  • ​What if my wife, who is taking 50,000 IU of vitamin D per day, gets pregnant one day?
  • ​Will she be able to continue with her high dose vitamin D therapy or would it be too dangerous for her?
  • ​And what about our baby?
  • ​Could large doses be harmful to him in any way?

That’s the kind of questions I sometimes worry about.

If you are pregnant or thinking about getting pregnant, finding satisfying answers to these questions is of the utmost importance.


That’s why I prepared this article and divided it into two parts.

In the first part, you’ll find a list of 6 of the reasons why supplementing with standard doses of vitamin D during your pregnancy is such a good idea.

In this way, you’ll feel much safer and confident about supplementation. 

I want you, and your future baby, to reap the benefits of vitamin D – and, believe me, there are many.

Then, you’ll be ready for the second part. In it, you’ll find the answer to the question raised in the title of this article.

Also, as a bonus, at the end of this post, you’ll find an important checklist. Can you tick all the boxes?

If so, you can be confident about starting – or maintaining – your high-dose protocol even while you’re pregnant.

P.s.: For your convenience all the cited studies are directly linked instead of appearing on a footnote.

Part ​​​​​1

​​Six reasons why you should be supplementing with standard doses of vitamin D during pregnancy

​1. There are only two supplements that even a healthy pregnant woman must take – and vitamin D is one of them

If you are pregnant or thinking about it, you are an easy target for advertisers.

You want the best for the developing child and you know how important vitamins and minerals are.

For these reasons, you can fall prey of aggressive marketing tactics attempting to persuade you to buy yet another supplement “for your future child’s sake – of course“. When you realize it, you have spent quite an amount of money.

But, ​was it money well spent?

It depends. Are you deficient in any nutrients?

If you are, then you need to take supplementation seriously. When a woman is pregnant, she’ll be “eating for two,” nutrients included. And, as it turns out, if there aren’t enough nutrients for the two of you, your body will tend to prioritize the baby. For example, your baby will get the calcium he needs, not by leeching it from your teeth (1) but from your skeleton. (2)

If, however, you are in good health, supplements could be a waste of your money – with two notable exceptions. At least, that’s the conclusion of an article published in the respected Drug and Therapeutics Bulletin (DTB).

According to the journal, “For most women who are planning to become pregnant or who are pregnant, complex multivitamin and mineral preparations promoted for use during pregnancy are unlikely to be needed and are an unnecessary expense.” (3)

What are the two notable exceptions?

The researchers added: “We found no evidence to recommend that all pregnant women should take prenatal multi-nutrient supplements beyond the nationally advised folic acid and vitamin D supplements.”

Folic acid and vitamin D.

What makes these two supplements so important?

Folic acid is essential to prevent your baby from developing serious health issues, such as heart problems and spina bifida (4) — a condition in which there’s no closure of the neural tubes. In addition, folic acid helps you too. Without enough folic acid you’d be at risk of developing anemia and peripheral neuropathy. (5)

But, what about vitamin D?

How important is it for both the mommy and the baby in her womb?

​If you are healthy, with the exception of folic acid and vitamin D, "complex multivitamin and mineral preparations promoted for use during pregnancy are unlikely to be needed and are an unnecessary expense."

Click to Tweet

​2. Vitamin D reduces your chances of suffering a miscarriage

The possibility of suffering a miscarriage must be one of the greatest fears a pregnant woman has to deal it, especially if such a terrible thing has already happened to her in the past.

As a man without kids, it’s hard for me to grasp the depth of the attachment soon-to-be parents develop for the unborn child. As such, the words traumatic and disheartening are most likely insufficient to describe the experience of going through a miscarriage.

Can vitamin D really help?

Recently, the Lancet Diabetes and Endocrinology journal published an uplifting study for women who had gone through the trauma of a miscarriage.

The paper states: “Sufficient preconception 25-hydroxyvitamin D (≥75 nmol/L) was associated with increased likelihood of pregnancy and livebirth. Increased vitamin D concentrations before conception, but not in early pregnancy, were associated with reduced pregnancy loss.” (6)

Or, in other words, if you have sufficient vitamin D levels before attempting to conceive a baby, you’ll not only increase the likelihood of actually getting pregnant but also the likelihood of a live birth.

The lesson is clear: For best results, supplement first, try to conceive a baby later.

​But what if you are already pregnant?

Will supplementation still be useful?

Yes, it will, as the next ​point clearly demonstrates.

Vitamin D increases your chances of conceiving, while reducing your changes of miscarriage.

Click to Tweet

​​3. Vitamin D significantly reduces the risk of your child being born with autism

Vitamin D is vital for any brain (7), but especially so for the one developing inside your child’s skull.

Currently, autism, mild or not, affects 1 in 68 people. Boys are four times more affected than girls. (8)

How would these statistics change if all mothers supplemented with an appropriate level of vitamin D during pregnancy?

Unsurprisingly, recent research shows a woman’s vitamin D level during pregnancy ​has a direct influence on her chances of giving birth to an autistic child. (9​, 10)

In one of the studies, involving women who already had at least one child with autism, the following vitamin D dosages were used:

  • ​5,000 IU daily during gestation, this dose being in most cases initiated only from the second quarter.
  • ​7,000 IU per day throughout the entire breastfeeding period. (Note that these 7,000 IU were taken daily by the mother, not by the child).
  • ​If the child stopped drinking the mother's milk, she (the child) would start supplementing with 1,000 IU daily until she was 3 years old.

For example, if the child suckled up to the age of 12 months, that would mean the child would start taking 1,000 IU of vitamin D from that point on and up to the age of 36 months.

After that period, researchers looked at the percentage of children who eventually developed autism. Then, they looked at the probability of these women having an autistic child — remember these are women who already had at least one autistic child.

What was the conclusion?

In normal circumstances, when a woman who has had a child with autism has another child, there's a 20 percent chance that this new child will develop autism. However, only 5% of the children involved in the study developed autism. That is, of the 19 children involved in the study, only 1 eventually developed autism. (11)

This was a study of small proportions, but it illustrates the potential of vitamin D when administered to the mother during pregnancy and breastfeeding period and to the child after this breastfeeding period ends and up until the age of 36 months.

​What if the child was already diagnosed with autism?

In another study, 106 children with autism who had blood levels of vitamin D below 30 ng/mL received a daily dose of vitamin D corresponding to 300 IU for each kilogram of body mass (300 IU per 2.20 pounds), but without ever exceeding a daily limit of 5,000 IU. 83 children completed 3 months of treatment. (12)

What was the result?

​67 of the 83 children who received vitamin D showed improvement in their autistic symptoms. 

76.1% of the children reported to have less symptoms of autism

Taking vitamin D during your pregnancy clearly benefits the baby. Therefore, even he does end up developing autism, it stands to reason that it would most likely be a milder form of the condition.

But does supplementing with vitamin D also benefits the mother?

​Supplementing with 5,000 IU of Vitamin D during gestation and 7,000 IU during lactation significantly reduces the chances of your baby ending up developing ​autism.​

Click to Tweet

​4. Vitamin D may reduce your chances of developing ​preeclampsia – pregnancy-induced hypertension

From an engineering point of view, pregnancy is an amazing period.

As the new being emerges inside your womb, countless changes occur in your body to provide him with all that he needs, including the formation of a new organ: the placenta.

This placenta will coordinate the “the exchange of nutrients and waste products between the maternal and fetal circulatory systems”. (13)

And, in order to bridge the gap between the placenta and the woman’s circulatory system, the body constructs a complex network of new blood vessels.

​What if, for some reason, this endeavor ​went wrong and this new mesh of blood vessels ​wasn’t properly assembled?

Then we would have a serious problem called preeclampsia.

Preeclampsia is the name given to a condition where the woman’s body is forced to raise ​its blood pressure in a desperate attempt to push the nutrient-filled-blood forward. This is done in the hopes that enough of it reaches the baby.

As you can see, the problem isn’t the high-blood pressure, per se. That’s just a symptom of a much bigger issue.

In certain cases, this lack of proper blood flow through and from the placenta can cause a cascade of health issues that can prove fatal to the woman, the baby or both.

Also, did you noticed there’s a “pre” in the word? That’s because preeclampsia can evolve to eclampsia. When entering ​this state of eclampsia, the woman will experience seizures.

Preeclampsia is estimated to affect between 2% and 8% of pregnancies. (14)

Could vitamin D reduce these statistics?

Many researchers believe so.

In “Systematic Review of Vitamin D and Hypertensive Disorders of Pregnancy” a group of Irish researchers stated that: “To date, trial evidence supports a protective effect of combined vitamin D and calcium supplementation against preeclampsia.” (15)

In another paper, researchers report giving 50,000 IU of vitamin D once every two weeks to a group of 72 pregnant women. At the same time, they had a control group of 70 pregnant women who received a placebo. This went on until the 36th week of pregnancy. (16)

Besides being pregnant, all these 142 women had one more thing in common: they had a history of preeclampsia.

How did the results from vitamin D supplementation compare with the placebo?

“The patients in intervention group have significantly lower probability of preeclampsia than patients in the control group. The risk of preeclampsia for the control group was 1.94 times higher than that for the intervention group.” Said the researchers.

In other words, vitamin D supplementation seemed to cut the risk of preeclampsia in half.

This lead this team of researchers to conclude: “The intended intervention (i.e., prescription of vitamin D) has a protective effect against recurrent preeclampsia. Vitamin D supplementation therapy in pregnancy could help in reducing the incidence of gestational hypertension/preeclampsia.”

​Vitamin D supplementation can ​cut ​your risk of ​pregnancy-induced hypertension (preeclampsia) in half.

Click to Tweet

​5. Vitamin D can lower your Risk of requiring a Cesarean Section by up to 400%

When a normal delivery is considered too dangerous, Doctors rely on C-Sections to perform a surgical delivery of the baby.

This medical procedure is much more common than I thought.

According to the data published by the CDC, in the year 2016, 31.9% were delivered through a C-section. (16)

31.9% of babies were delivered by C-Section

​This is unfortunate, because, even though this procedure can be life-saving, it’s still a major surgery with all its associated risks.

In this respect, I happy to report that vitamin D can help.

Here’s an example of an uplifting comment by a team of scientists investigating the association between vitamin D deficiency and primary cesarean section:

“In our analysis, women who were severely vitamin D deficient at the time of delivery had almost 4 times the odds of cesarean birth than women who were not deficient.“ (17)

Or, to restate this conclusion in a more impactful manner:

​If you aren’t getting enough vitamin D from sunbathing – or supplementation – you’ll be 400% more likely to require a C-Section.

​Are you vitamin D deficient? Than your baby is 400% more likely to ​be delivered through c-section.

Click to Tweet

​6. Vitamin D can reduce your chances of developing postpartum depression

The birth of a baby is a most anticipated event. You have been preparing for it for many months, imagining who the baby will resemble more and what his personality is going to be like.

However, all the chemical fluctuations occurring inside of you, coupled with all the social and psychological changes associated with caring for the new baby, can wreak havoc on your emotions and on your stress tolerance.

Although this is to be expected, it can also put you on the path to a kind of major depression named post-partum depression.

That’s where vitamin D can help.

Vitamin D has been found to be as effective as antidepressants. (18)

In Vitamin D and Depression: A Systematic Review and Meta-Analysis Comparing Studies with and Without Biological Flaws, a group of researchers got together to make an analysis of the many scientific studies examining the relationship between vitamin D and depression.

When these researchers focused on properly conducted studies, their conclusion was: "Meta-analysis of studies without biological flaws demonstrates that improving Vitamin D levels improves depression (...)" and "the effect size of Vitamin D demonstrated in our meta-analysis may be comparable with that of anti-depressant medication. (...). Should these results be verified by future research, these findings may have important clinical and public health implications."  (19) (Emphasis added) 

What dose of vitamin D was used?

By analyzing the various studies, these researchers found out that dosages ranged between 400 IU and 18,400 IU.

Based on these good results with standard depression, it isn’t surprising to find the following statements by another team of scientists who focused on postpartum depression:

“Low vitamin D during pregnancy is a risk factor for the development of postpartum depression symptoms.”


​“Women reported postnatal depressive symptoms at 3 days post-delivery. Women in the lowest quartile for 25(OH)-vitamin D status were more likely to report a higher level of postnatal depression symptoms than women who were in the highest quartile for vitamin D.” (20)

​"Improving Vitamin D levels improves depression."

Click to Tweet


These six reasons represent but a small sample of the potential benefits of vitamin D supplementation during pregnancy.

By making sure that your levels are within a healthy range, you’ll be reducing the chances of pregnancy-related complications while at the same time benefiting the developing baby.

This is especially true if you begin supplementing ​before ​attempting to conceive.

In fact, by continuing to supplement even during lactation you’ll continue to benefit your baby by ​further reducing his chances of developing autism.

​With this knowledge, we are now better enabled to tackle a much difficult question:

What about large doses?

Are they as benign as standard doses during pregnancy?

Part 2

​Are high doses of vitamin D safe during pregnancy?

If you are scared with the idea of taking a large dose of vitamin D you are not alone.

For example, remember those researchers who report how a dose of 50,000 IU of vitamin D once every two weeks reduced the incidence of preeclampsia?

At the end of their paper they decided to add this fascinating note:

During the present study, some participating patients were discouraged of participation in the study by nonmedical people and even some of clinical colleagues on alleged safety issues.”

Because of this, the researchers decided to meet with some of the gynecologists to address their concerns.

And we are talking about 50,000 every two weeks. That’s about 3,500 IU per day.

3,500 IU it’s nothing compared with the doses used in high-dose protocols such as the Coimbra protocol. Baseline doses may start around 40,000 IU per day and be increased in every appointment until the patient achieves significant relief.

Usually, this means reaching a dose of around 1,000 IU per Kg of body mass.

At the moment of writing, my wife takes 50,000 IU per day to keep the pain from ankylosing spondylitis under control. But there are reports of much higher doses being used.

Are these doses safe while you are pregnant?

It depends on several factors.

First of all, there's a key question that must be asked:

​Why are you taking high doses?

Most of the people undergoing a high-dose protocol are doing so because, like my wife, they have an autoimmune disorder.

This means their body is resistant to vitamin D. Or, in other words, as ​their body attempts to metabolize and activate vitamin D, it founds several issues preventing it from activat​ing all the vitamin D it intended. It's ​as if you​ owned a factory and asked for 10 items to be manufactured, but only 2 of the 10 ended up being produced well enough to be usable due to the poor workmanship.

For example, imagine someone named Alissa. Alissa has multiple sclerosis and, after several months on the Coimbra Protocol, her Doctor decides to raise her dose to 100,000 IU of vitamin D per day.

He doesn’t do this lightly, though.

This decision is based on Alissa’s lab results over the course of several months. On top of that, he trusts Alissa does her best to follow the safety guidelines. Therefore, the Doctor knows she’ll be safe with 100,000 IU.

Since Alissa’s tests were fantastic, he schedules their next appointment 6 months from now.

Compare this with Alissa’s best friend, Rosa. Rosa is a healthy woman and wants to stay that way for as long as she can. She loves to read about nutrition and is well aware of the benefits of vitamin D. In fact, she was the one who sold Alissa on the Coimbra Protocol. Rosa is also aware that a dose of 100,000 IU isn’t likely to become toxic right away. It may take a full month for the first symptoms of toxicity to appear.

Because of this and her excitement with Alissa’s results, Rosa begins supplementing with 100,000 IU on her own. A month flies by and she’s feeling great, so she decides to maintain her dose.

Months pass, and it’s now time for Alissa’s appointment. Her Doctor is thrilled with the results. Alissa is mostly asymptomatic, and it seems her multiple sclerosis is under control. He decides to maintain her on 100,000 IU for another six months.

What about Rosa?

Rosa is also at the hospital that day, but it’s being admitted to the ER. Doctors are shocked by her blood test results. Rosa’s calcium levels are way above the maximum value allowed by the reference range. She’s suffering from hypercalcemia and is about to become the subject of a scientific paper entitled “A 28-year-old woman with severe hypercalcemia: a case report.”

Now, let’s rewind to 3 months before.

Both Alissa and Rosa are thinking about getting pregnant. Should they?

Well, it’s true that both are supplementing with 100,000 IU of vitamin D per day, but would you give them the same advice?

Let’s look at each individual case.

Alissa is known to be resistant to vitamin D. This means her body is much more tolerant to higher doses. After all, most of that vitamin D that she’s taking won’t even end up being properly metabolized, much less activated.

Also, Alissa is doing regular blood and urine tests to make sure her calcium levels – and all the other relevant measurements – are within range.

Moreover, Alissa is well acquainted with the safety guidelines. She avoids calcium-rich foods because she knows vitamin D is promoting her intestine to absorb far more calcium from food than it normally would. This means she may get as much calcium from a serving of vegetables as she used to get from a glass of milk. In fact, drinking milk would be dangerous because of how it could cause her calcium levels to spike to a dangerous level.

Alissa is also careful about her daily fluid intake, making sure she drinks at least 2.5 liters of water every day.

On top of that, Alissa strives to walk regularly to stimulate her bones to reabsorb some of the calcium they are leeching due to vitamin D.

So, now that she is thinking about pregnancy, should she interrupt the protocol?

In her case, interrupting the protocol would allow her immune system to run awry again. This won’t just harm her nervous system, it may also endanger her baby. Why?

Because “both organ-specific and systemic autoimmunity are associated with an increased prevalence of recurrent miscarriage.” (21)

An out-of-control immune system increases your risk of miscarriage.

So, in Alissa’s case, supplementing with high doses of vitamin D while pregnant can be a good idea. She’s under the care of a knowledgeable Doctor and follows all the safety guidelines. She’ll be safe.

What about Rosa?

Rosa isn’t resistant to vitamin D. She has no specific reason to be taking such a high dose. By taking 100,000 IU every day for the last 3 months she’s putting herself at a real risk.

Worse, yet, she has been eating her regular diet, calcium-rich foods included.

Would it be a good idea for Rosa to keep taking this high dose of vitamin D while pregnant? Not a chance. In fact, Rosa should stop supplementing right now and measure at least her calcium blood levels for signs of vitamin D toxicity.

 The lesson is clear: Be more like Alissa and less like Rosa.

Should you take high doses of vitamin d while pregnant?

Yes, if you can tick all these boxes:

​High-Doses While Pregnant 
​Safety Checklist

  • ​Do you have a reason to be taking high doses of vitamin D, for example, a known autoimmune disorder?
  • ​Are you being followed by a qualified Doctor, familiarized with the high-dose Vitamin D protocols, and capable of adjusting your dose, as needed, throughout your pregnancy?
  • ​Have you been performing regular blood and urine tests to make sure that, at the very least, your calcium and PTH (Parathyroid Hormone) levels are within range?
  • ​Are you well-informed about all the safety guidelines and willing to follow them?
  • ​Are you aware of the vitamin D co-factors and taking them? These would include, at the very least, vitamin K2, vitamin B2, and magnesium.

If you answered yes to all these questions, then you can continue to take high doses of vitamin D while you’re pregnant.

If, however, you are doing the high-dose protocol on your own, it might be time to consider looking for medical help.

Unlike many proponents of supplementation, I’m not “anti-Doctors,” to the contrary, I believe a good Doctor can be a great ally. Of course, I also reckon that finding a truly good Doctor – and being able to pay for his services – can be challenging.

Nevertheless, if there’s a place for self-experimentation it’s certainly not when you’re pregnant.

If you are doing a high-dose protocol on your own and end up with hypercalcemia you can look for a Doctor, show him the lab tests you have been doing on your own, and ask him for help. You’ll get the adequate treatment and might even be able to get away with no permanent scars.

But if you are pregnant, a state of hypercalcemia is a tremendous challenge to the clinicians.

To put it bluntly here’s a quote from a paper published in 2016:

“Hypercalcemia in pregnancy is an uncommon event that can cause major maternal morbidity and/or fetal or neonatal morbidity and mortality. Management is a challenge for the clinicians, especially as regards to investigations in pregnancy, surgery, and the use of cinacalcet and bisphosphonates.” (22)

Hypercalcemia can kill you or your baby. It’s that’s serious.

That’s why high doses of vitamin D can only be taken by a mother who is under the care of a Doctor who knows what he or she is doing.

If you are on your own, your self-prescribed high-dose protocol may prove fatal to you or your baby.

Don’t be like Rosa, be like Alissa.

​Main takeaways from this article

  • ​Like folic acid, standard Vitamin D supplementation is essential while you are pregnant.
  • ​It reduces your chances of developing preeclampsia, postpartum depression or even of suffering a miscarriage.
  • ​It can even improve your odds of conceiving while also lowering your risk of requiring a C-Section.
  • ​It benefits your baby as much as it benefits you, by promoting the proper development of his nervous system and lowering his chances of developing autism.
  • ​For better results, you should start supplementing even before your first attempt at getting pregnant and continue to do so during lactation.
  • ​This standard dose might be of 5,000 IU per day, before and during gestation, and 7,000 IU per day during lactation​; or as directed by your Doctor.
  • ​Even though doses of up to 10,000 IU per day are generally considered safe without requiring any additional safety concerns (23​, 24, 25) they have not been tested for safety on pregnant women, so be sure to talk to your Doctor before taking this or any other supplement while you are pregnant.
  • ​During pregnancy, there’s no room for self-experimentation.
  • ​When you are pregnant, hypercalcemia, ​one of the main threats posed by high-dose Vitamin D therapy, can prove fatal to you or your baby. And, as rare as this tragic outcome might be, it’s not worth the risk. Don’t self-experiment while pregnant.
  • ​Higher doses of vitamin D – like the ones used in the Coimbra Protocol – should only be taken if prescribed, and as long as you remain under proper medical supervision.
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.