PCOS and Vitamin D: What do you need to know?

at a glance

PCOS and Vitamin D: What do you need to know?

In the world of nutrition, supplements, and health vitamin D seems to be the one thing we should obviously be getting enough of. Right?

I mean the combination of the sun and our skin should take care of our need. Wrong!

If you are reading this you probably have PCOS and chances are you have a vitamin D deficiency too. Yep, 67-85 % of people with PCOS have low vitamin d levels. (1)

Vitamin D has some pretty important jobs in the body – most of us think about vitamin D for bone health. Yet it does SO MUCH MORE than prevent you from needing a hip replacement in 30 years.

Right now vitamin D is acting in your body improving things like your immune health, metabolic health, heart health, and even your fertility.

Since you are likely to need some additional vitamin D let’s dig into what it is and why it matters with PCOS.


What is vitamin D?

Vitamin D is a nutrient our body can make and a nutrient that we eat. It’s not just a nutrient though. It’s a hormone. (mind blown, right?)

It has specific and REALLY important roles in sending messages from one part of the body to other areas and organs. (2)

Plants and fungi make vitamin D2 and humans and other animals make vitamin D3. Vitamin D is synthesized in the cholesterol in skin cells.

Most people do not live close enough to the equator to make enough vitamin D. Since we are increasingly concerned with skin cancer and cover our skin with hats, clothing and sunscreen we limit our body’s ability to make enough vitamin D.

Individuals with darker skin also struggle to make enough vitamin D, because the pigment in the skin acts as a barrier or shade. This limits the amount of sunlight our cholesterol is exposed to create enough vitamin D.

What food sources contain significant amounts of Vitamin D?

The food sources with the highest amount of naturally occurring vitamin D are:

  • cod liver oil

  • swordfish

  • salmon

  • tuna

  • sardines

  • liver

  • egg yolks

Most of us don’t eat these foods often enough to get sufficient amounts from food.

Since foods that contain vitamin D are limited the food industry fortifies (or adds) vitamin D as a nutrient to food that don’t have it already. The big ones are:

  • orange juice

  • milk

  • other dairy products

  • cereal

It is extremely common for us to have inadequate consumption of vitamin D rich foods and sun exposure to keep our vitamin D values in an optimal range.

Vitamin D Lab Values

In the United States levels are typically reported in ng/ml. Outside of the states, they are typically listed in nmol/l.

It is important you know what units were used in measurement because you could assume your vitamin D levels are great if they are at a 60. If it is really 60 nmol/l that is 24 ng/ml and if you compare that to the chart below it’s actually indicating a deficiency. However, if it is 60 ng/ml it is in the optimal range. Units matter!

Consider the chart below.

Severely Deficient: < 20 ng/ml ( < 50 nmol/l)

Deficient: 20-30 ng/ml (50-75 nmol/l)

Fair: 30-50 ng/ml (75-125 nmol/l)

Optimal: 50-80 ng/ml (125-200 nmol/l)

If you find yourself in the range less than optimal (which is likely) consider adding in a vitamin D supplement.

Optimal Dosing for Vitamin D and PCOS

What are the current vitamin D recommendations?

The current recommendation for vitamin D intake is 600(15 mcg) IU/day. Many researchers and nutrition experts have long regarded this level as being inadequate.

The current tolerable upper limit of vitamin D is 4,000 IU(100mcg) per day. Most people with PCOS will need to take more vitamin D in order to raise their level. Just as the current recommended intake is too low, research has shown no adverse effects when individuals take up to 10,000 IU per day.


Levels that show deficiency or severe deficiency:

After reviewing the data and concerns with low levels of vitamin D it is important to raise vitamin D levels to the optimal range with expediency. This is especially true if you are trying to conceive, have had a miscarriage, or struggle with insulin resistance.

Consider a product like Vitamin D Restore from PCOS Formularies. This product is a once-weekly dose of vitamin D3 in 50,000 IU levels. This is an aggressive dose and will be helpful for increasing numbers quickly.

Levels that show fair levels:

If you are within the fair range you will need somewhere between 2,000 IU and 4,000 IU of vitamin D3 daily.

When supplementing pills and sometimes add up quickly. Choosing a liquid vitamin D option can be helpful. It can also help to vary dosage as your levels improve you can adjust dosage without having to purchase an additional supplement.

Consider taking 4,000-6,000 IU if levels are in the 30-40 ng/ml range for 3-4 months.
Consider taking 2,000-5,000 IU if levels are in the 40-50 ng/ml range for 3-4 months.

What other nutrients help with vitamin D levels?

Many nutrients and vitamins have synergistic impacts on others.

The two that come to mind when taking vitamin D are magnesium and vitamin K.

Vitamin K and Vitamin D

We often think about bone health when taking vitamin D. It’s true, vitamin D is important to get calcium tagged and into the bones, however without vitamin K2 it can not do so effectively.
Vitamin K2 also has a really important role in making sure excess calcium does not get deposited in the artery.

Taking a blend of Vitamin D3 and Vitamin K2 is helpful when dosing with vitamin D for the long term.

Magnesium and Vitamin D

You literally will not be able to increase your serum(blood) levels of vitamin D if you are deficient in magnesium. So taking a magnesium supplement with your vitamin D will be helpful.

Magnesium also has important implications for PCOS as it can help improve blood sugar balance and most people with PCOS are deficient in it as well.

Magnesium is often found in foods, but evidence have shown that women with PCOS struggle to get adequate amounts in food and should consider a supplemental version. This is especially true if your vitamin D levels are not coming up with supplementing vitamin D alone.

Is it possible to get too much vitamin D?

It is possible but not common to have levels of vitamin D that are too high. This is in part because our body does a great job of regulating this if sun exposure is high. Most people’s diets are not optimized to eat vitamin D rich food sources in excess.

Unless supplementing with high amounts of vitamin D for long periods of time it can be difficult to get too much vitamin D. Working in healthcare for over 10 years I have literally never seen someone have vitamin D levels too high. However, I commonly see people severely deficient. In the context of PCOS this can be a big problem. Let’s dive into why.

How does low vitamin D affect PCOS?

Low levels of vitamin D are associated with common PCOS symptoms and health issues. Low vitamin d levels are inversely related to(that just means that this list I’m about to give is more common for those with low vitamin D levels):

  1. Insulin Resistance

  2. Ovulatory Dysfunction

  3. Infertility

  4. High Androgen Levels

  5. Obesity

  6. Heart Disease

  7. Mood Disorders

  8. Low Levels of Bone Density


PCOS and Bone Density

Bone density isn’t a super sexy thing to talk about. In the context of PCOS, it’s a big deal because progesterone is the hormone that helps to make sure we are making dense enough bones. No ovulation = no progesterone.

In a very critical period of our life (fertile years), we are put on birth control and we don’t make progesterone while on birth control. Those not on birth control do not cycle as regularly as women without PCOS and are exposed to much less progesterone.

So if we have low vitamin D levels and low progesterone(lack of ovulation) we are going to be on shaky ground as we age (figuratively and literally). Our body will not have the exposure needed to two hormones that play a critical role in bone health: vitamin D and progesterone.

This doesn’t need to be the case though. You can supplement with vitamin D and try to recover these levels and you can work on root cause factors to improve ovulation and progesterone production.

Vitamin D Levels Are Linked to Cycle Regularity

Low vitamin D status is related to irregular ovulation and longer cycles. In fact, those with normal vitamin D levels are 13.3 times more likely to ovulate in a cycle. (5)

There are some studies that have been done to assess if the genes that make it more likely to develop PCOS are linked with genes that make it more likely that you are vitamin D deficient. It seems there is some overlap in preliminary research.

Improving vitamin D levels has been associated with improved ovulation, pregnancy rates, and live birth rates.

How is vitamin D linked to fertility?

Did you know that your ovary has vitamin D receptors? How cool is that?! There are also receptors in the uterus and placenta.

It is common for women with PCOS to have high levels of a hormone called antimüllerian hormone (AMH). These high levels are typically associated with longer cycles and poorer egg quality.

When vitamin D levels are low AMH levels can be higher in someone with PCOS. Supplementing vitamin D helps to lower abnormally elevated AMH levels and can improve how follicles develop to be ready for ovulation. (3)

In one study looking at PCOS women in the context of fertility treatment there were three groups:

  1. taking metformin alone

  2. taking metformin + calcium + vitamin D

  3. taking calcium and vitamin D alone

It was found that the group taking vitamin D, calcium, and metformin had the most improvement in dominant follicles and pregnancy rates. (4)

Vitamin D levels are known to improve natural pregnancy, treatments with ovulation-inducing medicines like metformin and clomid, and IVF success.

The goal isn’t getting pregnant for most people, right? We want to stay pregnant and have healthy babies.

Is vitamin D also important during pregnancy?

Vitamin D levels that show deficiency increase the risk of pregnancy loss.

Early Pregnancy Loss

This is especially the case in first-trimester loss. In fact, someone who has a history of first-trimester pregnancy loss, that has a vitamin D deficiency is more likely to have subsequent pregnancy losses. (6)

Pregnancy Complications

Pre-eclampsia and pre-term birth are more likely in someone who has a low vitamin D status.

These are modifiable risk factors which is encouraging because not everything that increases the risk of pregnancy loss or complications is modifiable (like genetics). Yet, taking vitamin D supplements is safe, inexpensive, and easily done.


Vitamin D and Mental Health Conditions

Vitamin D insufficiency is related to depression in women suffering from PCOS. Vitamin D has long been known to impact risk of mental health.

Being that women with PCOS are more likely to struggle with depression and anxiety, and low levels of vitamin D are also correlated with these conditions, it’s important to have vitamin D levels regularly checked and supplement accordingly.

Does Vitamin D affect Metabolism?

Vitamin D has been linked to inflammatory diseases like obesity, diabetes mellitus, insulin resistance, and heart problems, including hypertension.

Several studies have found vitamin D deficiencies may be associated with the development of metabolic syndrome risk.

Vitamin D plays a role in insulin signaling and can help impact overall inflammation levels. Taking a vitamin D supplement may help with improving insulin response.

Can Vitamin D Help Reduce Inflammation?

Women with PCOS have higher levels of inflammation compared with age and BMI-matched women from the general population.

Supplementing with 4,000 IU/day for 12 weeks showed a reduction in total testosterone and a reduction in hs-CRP which is an inflammatory marker. (7)

This was compared to a placebo group and a group supplementing with 1,000 IU/day. You’ll remember that the RDA for vitamin D is 600 IU/day. I think we need to really consider that women with PCOS probably need more than the general population for MANY reasons.

Hands up if you want to see inflammation and testosterone levels go down!


Discount on Vitamins for Reading this Blog

Head to PCOS Formularies and purchase either Vitamin D Restore or Optimal Vitamin D – then you will get 10% off Optimal Magnesium when you use code: VitaminDBLOG.



1 Thomson RL, Spedding S, Buckley JD. Vitamin D in the aetiology and management of polycystic ovary syndrome. Clin Endocrinol (Oxf) 2012;77:343–50.

2 Harvard, The Nutrition Source, Vitamin D

3 Irani M, Merhi Z. Role of vitamin D in ovarian physiology and its implication in reproduction: a systematic review. Fertil Steril. 2014 Aug;102(2):460-468.e3. doi: 10.1016/j.fertnstert.2014.04.046. Epub 2014 Jun 3. PMID: 24933120.

4 Rashidi B, Haghollahi F, Shariat M, Zayerii F. The effects of calcium-vitamin D and metformin on polycystic ovary syndrome: a pilot study. Taiwan J Obstet Gynecol. 2009 Jun;48(2):142-7. doi: 10.1016/S1028-4559(09)60275-8. PMID: 19574176.

5 Singh, Vinita, et al. “Association between serum 25-hydroxy vitamin D level and menstrual cycle length and regularity: A cross-sectional observational study.” International Journal of Reproductive BioMedicine 19.11 (2021): 979

6 Louise B Andersen, Jan S Jørgensen, Tina K Jensen, Christine Dalgård, Torben Barington, Jan Nielsen, Signe S Beck-Nielsen, Steffen Husby, Bo Abrahamsen, Ronald F Lamont, Henrik T Christesen, Vitamin D insufficiency is associated with increased risk of first-trimester miscarriage in the Odense Child Cohort, The American Journal of Clinical Nutrition, Volume 102, Issue 3, September 2015, Pages 633–638,

7 Jamilian, Mehri, et al. “Effect of two different doses of vitamin D supplementation on metabolic profiles of insulin-resistant patients with polycystic ovary syndrome.” Nutrients 9.12 (2017): 1280.



The advice provided in this article is for informational purposes only. It is meant to augment and not replace consultation with a licensed health care provider. Consultation with a physician, dietitian, naturopathic doctor or other primary care provider is recommended for anyone suffering from a health problem.

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