woman drinking water by pool

Will Vitamin D help or hurt you if you have Mast Cell Activation Syndrome or Histamine Intolerance?

If you have Mast Cell Activation Syndrome or Histamine Intolerance, you may need to look at Vitamin D!

Vitamin D is actually a hormone, not a vitamin. But it is still commonly called a Vitamin, so I’ll use the common term Vitamin D here.

Low Vitamin D is thought to be involved in many immune conditions, including mast cell disorders (Theoharides, 2017).

Vitamin D has many roles in the body. In the context of Mast Cell Activation Syndrome, vitamin D:

  • stabilizes mast cells
  • regulates the immune system
  • functions as an anti-inflammatory (Liu, Z.Q, et. al, 2017) (Conti & Kempuraj, 2016).

Wow! This means we really need to be paying attention to Vitamin D. In my practice, I’ve noticed that 90% of people who aren’t supplementing with Vitamin D who have Mast Cell Activation Syndrome have low levels. And even those who are supplementing often aren’t taking enough.

But because Vitamin D is a hormone – we don’t want to guess about this! It is very important to check your levels the right way and find out what you need. Then you need to do follow-up testing to make sure your supplement levels are appropriate for your body.

Mine were actually very low. I had noticed I always felt so much better during a vacation to a sunny location. When I finally got the right Vitamin D testing (doctors kept ordering the wrong one) – I saw it was really low. Supplementing has helped my Mast Cell Activation Syndrome and Histamine Intolerance a lot.

Will it help you? Let’s find out! First, you have to check your levels…

Please note, this blog post is for informational purposes. If you have a medical condition, please discuss your Vitamin D levels with your medical provider.

How to check for Vitamin D levels in Mast Cell Activation Syndrome or Histamine Intolerance

When you go to get your Vitamin D checked, there are 2 options for Vitamin D testing.

Here is the wrong option for checking Vitamin D levels in Mast Cell Activation Syndrome or Histamine Intolerance:

Most traditional doctors test Vitamin D with a test called 1,25(OH)₂D also called a Vitamin D 1,25 Dihydroxy (Calcitriol) Blood Test. This test measures active Vitamin D produced in the liver and kidneys.

Sounds good, right? The problem is this test usually shows normal results even if your storage levels of Vitamin D are too low. It is really only useful in severe kidney and parathyroid issues. So, even though this is the one most often ordered, it isn’t likely this test is going to help you! This is a very common and inappropriate misunderstanding among a lot of practitioners.

Why would this be??? The UC Davis Medical School website reports this is because:

“The root causes for inappropriate 1,25 dihydroxyvitamin D ordering include:

(a) clinicians not understanding the biological role of 25-OH versus 1,25 dihydroxyvitamin D, or

(b) 1,25 dihydroxyvitamin D showing up as the “first” orderable test on electronic medical record (EMR) systems.”

Sheesh! That’s a pretty big misunderstanding! These kinds of misunderstandings are rampant in Traditional Healthcare, unfortunately. And this is one of the more benign kinds of misunderstanding that happen. They can get much worse.

This is why people with Mast Cell Activation Syndrome or Histamine Intolerance rarely improve with Traditional Healthcare. One reason is you have to get the right tests. And these aren’t usually ordered.

I could go on a long rant here. But I don’t want to get off topic, so I’ll reign it in for now.  Just know you have to strongly advocate for yourself in Traditional Healthcare because that system is badly broken. But, back to Vitamin D…

So, what should you do to accurately check your Vitamin D levels?

Here is the right option for checking Vitamin D levels in Mast Cell Activation Syndrome or Histamine Intolerance

Functional practitioners understand the biological roles of these types of Vitamin D and the different tests. So, Functional practitioners recommend a Vitamin D 25(OH). This is the best way to check your Vitamin D levels. This test is also called D-25-hydroxy or sometimes, calcidiol 25-hydroxycholecalcifoerol.

So, make sure your practitioner is getting this for you. Or if you want to work with me, you’ll be guaranteed to have the right test recommendations.

How to interpret the results of Vitamin D testing in Mast Cell Activation Syndrome or Histamine Intolerance

So, once you get your Vitamin D 25(OH) test back, you may face another hurdle. The standard lab ranges for deficiency are way too low!! The standard lab range says anything >30 ng/ml is normal.

This simply isn’t true, though. In immune issues like Mast Cell Activation Syndrome and also in Histamine Intolerance, you are looking for a range between 60 and 100. That’s double the “normal” lower limit of the labs!

If you know you have VDR genetic variants, you should definitely keep an eye on your Vitamin D25(OH) levels through testing. Even if you do get plenty of sun exposure a day.

So, bottom line: make sure you get the right tests AND it is being reviewed with the appropriate functional ranges.

But what if your levels come back lower than 60…?

What to do if your Vitamin D levels are low and you have Mast Cell Activation Syndrome or Histamine Intolerance

One of the best ways to get Vitamin D is through daily sun exposure, if possible, without burning. This means you have to get at an absolute bare minimum 10 minutes of sun exposure midday without sun screen. This is rarely enough, though. You’ll need closer to 20-30 minute of sun between 10am and 2pm. You need even more time in the sun the darker your skin is.

And you have to get this exposure every day of the year. If you live in a climate with cold winters, getting sun exposure may not be possible year-round.

Unfortunately, many people with Mast Cell Activation Syndrome are heat and sun sensitive. So, even if you live in a warm, sunny location, this may still not work for you.

So, what to do???

In these cases, Vitamin D supplementation may be necessary if your Vitamin D levels are low.

But first, don’t use the D2 form. This is a very cheap form of D2 that is the inactive type. It doesn’t convert well and doesn’t do a great job of raising D25OH levels.

You want to supplement with the active form D3. D3 is better absorbed when paired with K2 and taken with food. It is usually taken in the morning.

If you have any kind of clotting or bleeding disorder or take medications for these, you need to talk to your doctor before using K2. If you have significant menstrual clotting, you may not want to take K2 the week of their period.

How much D3 should you supplement when you have Mast Cell Activation Syndrome or Histamine Intolerance?

It really depends on a number of factors:

  • What were your D-25(OH) levels?
  • How much sun exposure do you get? Can you increase it?
  • Do you have osteopenia or osteoporosis?
  • Are your minerals balanced?

This means you’ll probably need a functional practitioner to help you figure out your exact dosages. The vast majority of people can safely start with 1,000IUs of D3 per day. This likely won’t be enough, but you could start here until you can check with your practitioner. Or if you have Mast Cell Activation Syndrome or Histamine Intolerance, you are welcome to book a Mast Cell 360 Case Review with me. I’ll help you sort it out as well as dive deeply into your case.

Now, how do you pick out a Vitamin D Supplement…?

Which Vitamin D brands are good when you have Mast Cell Activation Syndrome or Histamine Intolerance?

Remember how I mentioned before Vitamin D is really a hormone? This is why I insist my clients use a pharmaceutical grade brand. Pharmaceutical grade supplement companies use 3rd party testing to ensure accurate levels. Less reliable brands don’t guarantee the quantity or quality of their supplements. So, you could get 10x what it says on the bottle in a capsule one day and have 0 amount of the supplement in a capsule the next day.

Fortunately, even pharmaceutical grade Vitamin D3 doesn’t cost much more than the cheaper brands. Here are 2 brands I recommend:

Inwell Biosciences Vitamin D3 With K2:

Pure Encapsulations Liquid Vitamin D3 without K2:

Rechecking Your Vitamin D Levels in Mast Cell Activation Syndrome and Histamine Intolerance

Once you’ve been supplementing for 3-6 months, you definitely need to get your Vitamin D levels re-checked.

This is because of 3 reasons:

  1. You want to make sure you are supplementing with enough Vitamin D to hit the optimal range.
  2. You want to make sure the Vitamin D you are taking is getting absorbed and working for you.
  3. You want to make sure you don’t overshoot the optimal range.

It is really better not to guess. I’ve seen people getting sun exposure daily PLUS taking 10,000IUs of Vitamin D still have low levels. That tells me there is an absorption and cofactor issue. Once we fixed those issues, the Vitamin D levels became optimal.

The other reason is that I’ve worked with people who had been put on 5000 IUs, which is usually considered very safe. They hadn’t been rechecked and thought they were fine. When I insisted we re-check the D25(OH) levels, it came back well over 100. They were greatly overshooting the optimal range! Just as too low Vitamin D can be a problem, so can too high.

So, just make sure you are getting it rechecked. Even paying out-of-pocket, it is a cheap test.

Once you hit the optimal range, I recommend rechecking Vitamin D25(OH) once a year.

Bottom Line on Vitamin D in Mast Cell Activation Syndrome and Histamine Intolerance

  1. Test your levels with the right test – D25(OH)
  2. Check your results with the right reference range – you want to be between 60 and 100 (unless you have liver or kidney disease)
  3. Work with a Functional Practitioner to figure out your optimal dose.
  4. You can safely start at 1000IU, but will likely need more.
  5. Only use D3. Take with food in the morning. Take with K2 if you can, for better absorption.
  6. Only use pharmaceutical brands because this is a hormone. (See brand recommendations above.)
  7. Retest to make sure your levels are improving and in the optimal range.

If you need help with your Mast Cell Activation Syndrome and Histamine Intolerance, you are welcome to book a Mast Cell 360 Case Review for a thorough dive into your health issues, get a step-by-step action plan, and start getting results.

More Mast Cell Supporting Supplements


Conti, P., & Kempuraj, D. (2016). Impact of Vitamin D on Mast Cell Activity, Immunity and Inflammation. Journal of Food and Nutrition Research, 33-39.

Liu, Z.Q, et. al. (2017). Vitamin D contributes to mast cell stabilization. Allergy, 1184-1192.

Theoharides, T. (2017). Vitamin D and Atopy. Clinical Therapeutics, 880-881.

Tran, Nam K. Vitamin D Testing: Is it 25-OH or 1,25-Dihydroxy? Laboratory Best Practice Blog. Accessed 9/5/2019

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  1. Elise

    My Vit. D levels are very low and have tried many different types of supplements. The supplements trigger my symptoms more than almost anything. I will be ordering some from the site above and hope it will be better.
    Thank goodness that the sun is not a trigger for me, but I need more.
    Great information, thanks

    1. Beth O'Hara

      Hi Elise – if you’ve tried very clean sources of Vitamin D, there may be something else going on. Have you had your thyroid and parathyroid checked? Have you checked RBC Magnesium? These reactions are also common in mold toxicity and Lyme. I recommend you make sure to look into the underlying root issues before trying Vitamin D again. You can let me know if you need help with checking root causes.

    2. san mck

      Are you saying that vitamin d triggers your histamines?

      1. Beth O'Hara

        You want to be sure to have the right levels and use the right kind of supplements.

  2. Jodi

    Yeah I reacted horribly to sun over a 2 day period and i wasn’t out for long and it was in April in the Midwest, I couldn’t be in the sun for 6 weeks after that. I also have other conditions, EDS, pots,
    Possible endometriosis,
    Severe Tmj and mast cell and mold sickness, my body doesn’t seem to tolerate d inside a bottle, I used d3/k2 by orthomolecular brand, just 1 drop, I feel like I’m on speed, my d level done by functional med dr a year ago was at an 8, also the main ingredient in vitamin D that Starts with a C, its in rat poison, just an FYI. Spreading the word.

    1. Beth O'Hara

      Hi Jodi – These kinds of reactions can happen in significant mold toxicity and Lyme. I would recommend you address the mold toxicity first before trying Vitamin D again in any form. You are correct that D is used in rat poison – in extremely higher concentrations that a person would ever take. Similarly, even water would be toxic if you consumed 50 gallons at a time. This doesn’t mean we want to stop drinking water or using Vitamin D at the right dosage. Once your mold toxicity is cleared up, you will likely tolerate Vitamin D in normal doses.

  3. Andreas Schindhelm

    Hello Beth, at first thank you for all your information you share with us!

    Most D3 supplements are MCT Oils, but my mast cells are freaking out on any coconut products… can you recommend any other form?

  4. Alison Larson

    Hi Beth,
    I’m concerned I have been reacting to the source of my Vitamin D (lanolin). I did not bother to ever look at the source of most vitamin D, and when I did I just about fell out of my chair. I have huge skin reactions to lanolin & have avoided it for years, only to discover I’ve been ingesting it now for many months–and I’m experiencing a bunch of MCAS symptoms and at my whits end. What do you recommend for an alternative source for vitamin D? I’m trying to learn what the injections are made of, but that’s proving to be challenging. I also struggle with vitamin C (ascorbic acid seems to be very problematic, making me feel like my body is doing the fizzing!), so supplements are quite difficult. Any suggestions?
    Thank you,

    1. Suz, Mast Cell 360 Team

      Hi Deana,
      Beth typically stays away from soy, but you might want to contact the manufacturer to be sure.

  5. Kristen Abrahams

    Hi there!

    I unfortunately have Lyme, Babesia, Mold, and an Alpha-gal allergy (red meat allergy).

    I was taking the Inwell D3 K2, but I started to have a reaction to it. I called the manufacturer and it turns out it has lanolin in it (which carries the alpha-gal sugar molecule).

    I’ve been lucky to find supplements for everything except D3 K2. I talked to my integrative medicine doctor, but he did not really have an answer for me.

    Is there any chance you might know of a 100% vegan D3 K2 supplement? I see Mary Ruth’s has one sourced from lichen, but it is not medical grade.

    1. Suz, Mast Cell 360 Team

      This is the vegan D3 Beth uses in the practice: https://us.fullscript.com/product_cards/79068/redirect?store_slug=mastcell360

      This is the D3K2 but I’m not sure if it is vegan. You can contact the manufacturer to see. https://us.fullscript.com/product_cards/82840/redirect?store_slug=mastcell360

      And always be sure to talk with your doctor to see if anything new will be right for you. If you decide to try these products, you can use either of the links provided to register an account and you will save 15% off all your orders through FullScript.

      I hope this helps!

  6. Kristen Abrahams

    Thank you for the info! Just so you know, I contacted the bioprotein manufacturer and it does in fact come from lanolin. I’ll use the other D3 you listed 🙂

  7. Sharon

    Is the Lichen version not act like mold? I remember reading a review of a lichen type powder from vitamin D and the person got a bad reaction because she says lichen is similar to mold. Thank you.

    1. Suz, Mast Cell 360 Team

      Hi Sharon,
      Lichen is a plant, not a fungus like mold. It isn’t at all like mold. I haven’t seen this be an issue for our clients.

  8. Elly

    Could you elaborate more on the relation of Vitalmin D to thyroid, parathyroid problems and RBC Magnesium?

    1. Suz, Mast Cell 360 Team

      Hi Elly,
      Thanks for your interest in Mast Cell 360! This is more than we can go into in a response here, but we are always adding new material to the blog about a variety of topics related to Mast Cell Activation Syndrome and Histamine Intolerance. In the new year, we’ll have lots of new posts!

  9. Julie


    I can’t seem to be able to buy the vitamin d3 with k2 that you recommend. Do I have to go through you?

    Thank you

    1. kam

      Hello Julie,

      Thanks for reaching out. You can purchase the Inwell Biosciences Vitamin D3 + K2 referenced above at this link:


      If you’d prefer a liquid that can be titrated up, we also see many people do well with this one:


      You’ll need a Fullscript account to order things we suggest from Fullscript. They never charge more for the products through that link, as a matter of fact, it will save you 15%! And it helps support our free information on the website and Facebook. We aren’t familiar with your case and can’t say what may be right for you. So, please discuss changes with your practitioner.


  10. Mirna

    Hello there! I just stumbled over this article in search for a good vit d3 and k2 source – I noticed having issues with combo products as k2 seems to be mostly derived from fermented nato here in EU. How can we properly supplement with K2? This seems to really be an issue for people with mcas or hi!
    Thank you,

    1. kam

      Hello Mirna,

      I’m sorry to hear you’re having a difficult time with the k2. We don’t have any resources specifically on that at this time. But this is a D3+K2 often used in the clinic that we’ve had good success with: https://us.fullscript.com/product_cards/91967/redirect?store_slug=mastcell360

      You’ll need a Fullscript account to order. They never charge more for the products through our links and it will save you 15% on anything! It also helps support our free content on the website and Facebook. They don’t ship internationally, though, and you would need an intermediary like http://www.MyUS.com that some of our customers use. We don’t vet shipping companies, so this is just an idea we’ve gathered from others for your consideration.

      And please always speak with your practitioner about any changes in supplements.


  11. Christie

    I react badly to anything with the alpha gal protein (waiting on testing for that), so I can’t do lanolin-derived D3. And every single type of algae-derived D3 I’ve tried has given me a histamine reaction (even small amounts of D3, just like the spirulina reaction I had). Are there any options left besides going out in the sun? My D3 is low and I’ve been trying really hard to bring it up, just dealing with the pain from the histamine reaction but I can’t continue this way. I’m at a loss. I do have a practitioner I’m working with but she’s at a loss now too. My symptoms are very well controlled and I feel great, but I have the hardest time adding new supplements or foods back

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