Vitamin D

Vitamin D (most supplements are D3 / cholecalciferol) functions more like a hormone than a typical vitamin. After intake (or skin production from sunlight), it is converted in the liver to 25-hydroxyvitamin D (25-OH D) and then in the kidneys (and some other tissues) to calcitriol, the active hormone form. Calcitriol binds the vitamin D receptor (VDR) and influences gene expression across many systems, including calcium/phosphate balance, immune signaling, inflammation, and in some contexts mood and energy regulation. Because it is hormonally active, baseline level and dosing matter, and higher doses are not always better.

In PFS/PSSD/PAS discussions, vitamin D is often viewed as a “basic” supplement—especially when correcting a documented deficiency—but there are also anecdotal reports of symptom flares in a subset of already-sensitized individuals. Reported issues include worsened anxiety, sleep disruption, fatigue, or sexual symptoms after supplementation. The mechanism is not established, and many people tolerate vitamin D well or feel better when deficiency is corrected. A commonly suggested harm-reduction approach in these communities is to check a 25-OH vitamin D level first, start with a lower dose if needed, change one variable at a time, and stop if a clear, consistent worsening occurs—ideally with clinician guidance, particularly if other hormone-active supplements are also in use.

Crash Anecdotes (Community Reports):

https://www.reddit.com/r/PSSD/comments/1ibo9hz/vitamin_d_i_feel_makes_my_symptoms_worse/

https://www.reddit.com/r/FinasterideSyndrome/comments/1alh3x1/vitamin_d/

How to Interpret This Page

This page summarizes anecdotal reports and community observations, not medical evidence. “Risk” here refers to how frequently severe or prolonged symptom worsening is reported, not to proven causation or population-wide probability. Individual responses vary widely, and absence of issues in some users does not rule out significant reactions in others.

Risk Signal Based on User Reports

Reports of Symptom Worsening in Some Users (for PFS/PSSD/PAS):
Among individuals who already have PFS/PSSD/PAS, vitamin D supplementation is occasionally mentioned in community reports as preceding symptom flares. Many users report neutral or beneficial effects—especially when correcting deficiency—but a subset describe anxiety, sleep, fatigue, or sexual-symptom changes after supplementation. Because vitamin D is hormonally active and dosing varies widely, some in the community prefer a cautious approach: confirm deficiency with labs, use the lowest effective dose, and avoid stacking multiple new hormone-active supplements at the same time.

For individuals without these conditions, vitamin D is widely used and generally well tolerated, with the most common concerns relating to excessive dosing (e.g., hypercalcemia risk) rather than PFS/PSSD-like symptoms. Still, given individual variability and the uncertainty described in some anecdotes, some people judge careful dosing and lab-guided supplementation to be prudent.

Evidence basis: Anecdotal reports (online forums, self-reports); established physiology of vitamin D metabolism; no controlled studies examining PFS/PSSD/PAS-specific outcomes.