A 2024 systematic review (Lackner et al., Acta Dermato-Venereologica) identified seven studies covering 575 HS patients. In all seven, HS patients were vitamin D deficient. Serum vitamin D levels negatively correlated with disease severity across included studies. A 2026 systematic review and Mendelian randomisation analysis (Spiteri et al.) confirmed this pattern across 12 studies.
What the research actually shows
The deficiency finding in HS is one of the most consistent patterns in the nutritional literature for this condition.
The 2024 systematic review (Lackner et al.) included three cross-sectional studies, two pilot studies, one controlled cohort study, and one prospective case-control study. All seven found deficiency in HS patients. Serum vitamin D levels negatively correlated with disease severity, meaning lower levels were associated with more severe HS. A randomised controlled trial specifically on vitamin D and HS severity is still needed to move from correlation to confirmed causation.
The 2026 analysis by Spiteri et al. used a two-sample Mendelian randomisation approach from the UK Biobank. Results were suggestive of a causal direction, but did not definitively resolve it. Both directions likely operate simultaneously: low vitamin D may worsen HS, and active HS may deplete vitamin D.
Why vitamin D matters specifically for HS
Vitamin D functions more like a hormone than a classical vitamin and plays a direct role in immune regulation.
Vitamin D receptors (VDR) are present on virtually every immune cell in the body: T cells, B cells, macrophages, and dendritic cells. These are the exact cells driving the chronic, dysregulated inflammation in HS. When vitamin D is deficient, regulation of these cells is compromised.
Vitamin D also supports keratinocyte function directly. Follicular keratinocyte health is central to the starting point of HS: follicular occlusion. Anything that supports follicular integrity is mechanistically relevant to how frequently that starting point is triggered.
How common is vitamin D deficiency in HS patients?
The deficiency finding is replicated across studies from different countries and research groups. HS patients generally show lower adherence to Mediterranean-style dietary patterns, higher consumption of ultra-processed foods, and lower physical activity levels than matched controls — all independently associated with lower vitamin D status.
Sunlight exposure, skin pigmentation, body fat distribution (vitamin D is fat-soluble and can be sequestered in adipose tissue), and certain medications can also affect status. Many people with HS arrive at a compromised vitamin D baseline before any supplementation is considered.
Does vitamin D supplementation improve HS?
The deficiency correlation data is strong. The direct intervention evidence, showing that supplementing vitamin D improves HS outcomes, is weaker. No large randomised controlled trial has been completed specifically to test vitamin D supplementation in HS.
What can be said with confidence: correcting vitamin D deficiency supports the immune function and inflammatory regulation pathways that are directly implicated in HS. Allowing a known, correctable deficiency to persist when it is consistently documented in this population does not make clinical sense.
This is not the same as saying "vitamin D will improve your HS." It is saying that having adequate vitamin D levels is a reasonable and evidence-supported component of an overall approach.
What dose is appropriate?
Vitamin D3 is the form consistently shown to maintain serum levels more effectively than vitamin D2. For maintenance supplementation in adults, 2,000 IU daily is a standard dose appropriate for chronic daily supplementation. If you are clinically deficient, higher loading doses under clinical supervision may be appropriate to correct status before dropping to a maintenance level.
Vitamin D is fat-soluble. It is best absorbed when taken with a meal containing dietary fat. A serum 25-hydroxyvitamin D test is the standard way to measure your current status.
Getting tested: what the numbers mean
Standard reference ranges for vitamin D status:
- Severely deficient: below 30 nmol/L (below 12 ng/mL)
- Deficient: 30-50 nmol/L (12-20 ng/mL)
- Insufficient: 50-75 nmol/L (20-30 ng/mL)
- Sufficient: above 75 nmol/L (above 30 ng/mL)
Many HS patients who have never been tested are likely sitting in the deficient or insufficient range without knowing it.
What vitamin D cannot do
It cannot replace prescribed medical treatment. At Hurley Stage 2 or 3, biologics, antibiotics, hormonal therapy, and surgery address HS through mechanisms that vitamin D cannot match.
It also does not work immediately. Correcting deficiency and reaching adequate serum levels takes weeks to months of consistent supplementation.
HS Daily includes vitamin D3 at 2,000 IU per daily sachet, a standard maintenance dose appropriate for a population where deficiency is near-universally documented. It is not a treatment for HS. It is structured nutritional support designed to work alongside whatever your dermatologist has prescribed.
For more on the broader nutritional deficiency picture in HS, see our post on what vitamin deficiencies are common in HS patients (add URL when Post #14 publishes)
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Frequently asked questions
How do I know if I'm vitamin D deficient?
The standard test is a serum 25-hydroxyvitamin D blood test. Your GP or dermatologist can order it. Sufficient levels are generally considered to be above 75 nmol/L. Given the consistent deficiency finding in HS research, this is worth checking even if you have no specific symptoms.
Can I get enough vitamin D from sunlight?
The amount varies significantly based on skin tone, latitude, season, and sun exposure duration. People with darker skin tones, those at higher latitudes, and those who avoid sun exposure are at higher risk of deficiency. Supplementation is the most reliable way to correct and maintain adequate status.
Is vitamin D safe to take long term?
Vitamin D3 at 2,000 IU daily is considered safe for most adults for long-term use. Very high doses above 10,000 IU daily for extended periods can cause toxicity, but this is not a concern at a standard 2,000 IU maintenance dose.
Does vitamin D interact with HS medications?
Vitamin D supplementation is not known to interact negatively with the biologics, antibiotics, or hormonal therapies commonly prescribed for HS. Always confirm with your prescribing clinician when adding anything to your regimen.
Will vitamin D stop my HS flares?
No evidence supports this claim. Correcting vitamin D deficiency supports immune regulatory pathways implicated in HS, but it is not a flare-prevention strategy on its own.
This article is for educational purposes only. It is not a substitute for medical advice. If you have hidradenitis suppurativa, work with a board-certified dermatologist to build a treatment plan.
References
- Lackner L, Zyriax BC, Stephan B. To what extent does vitamin D influence the severity of hidradenitis suppurativa. Acta Derm Venereol. 2024. https://pubmed.ncbi.nlm.nih.gov/39254290/
- Spiteri J, et al. Investigating the inflammatory link between vitamin D and hidradenitis suppurativa. Int J Mol Sci. 2026. https://pubmed.ncbi.nlm.nih.gov/41898761/
Published by HS Daily.
