Not Medical Advice: This content is for general information and educational purposes only and isn’t a substitute for professional medical guidance. Always consult a qualified healthcare provider before making changes to your health, diet, supplements, or training. Reliance on any information from this blog is solely at your own risk.
Everything below is strictly based on my own personal experience.
My vitamin D levels
In many online health and longevity spaces vitamin D levels are debated and dissected on the regular. The optimal levels, the number of IUDs to supplement, and the life-changing narratives people had when increasing their dosage all began to wiggle into brain. Adding to this, news articles were published stating a large percentage of the world has a vitamin D deficiency which may be negatively affecting our health since vitamin D deficiency is associated with cancer and chronic diseases. Was I one of those people? Should I be increasing my vitamin D intake?
I had never thought much about my vitamin D levels nor had it ever been suggested by a doctor to have my labs tested for it. I assume this was so since I never had any symptoms of low vitamin D, I’m not one of the populations most likely to suffer from a deficiency, and that particular test is not usually included with annual bloodwork. I also live in an area with easy, year-round access to the sun’s UVB rays which allow my body to synthesis vitamin D naturally without supplementation.
Although knowing I was unlikely to be deficient, perhaps increasing my levels would bring me some unforeseen benefits, such as higher energy or better sleep. I wouldn’t know unless I tried. Since vitamin D is an inexpensive supplement, easy to take, and with few side effects, it only seemed natural that I should do some self-experimentation.
Following my decision to supplement, I picked up some vitamin D3/K2 pills (1000 IUD daily) from my local drug store about a year ago and began to take them regularly with some fats, such as nuts and seeds, to help with absorption. This went on for months until I realized that if I’m not testing my vitamin D levels, then I don’t know if it’s having any internal affect (positive, neutral, or negative) or if I simply wasting my money and possibly doing a disservice to myself. I should at least know if my vitamin D level was increasing with supplementation.
In June of 2025, I took my first vitamin D test, VITAMIN D,25-OH,TOTAL,IA, which I paid out of pocket for (around $45 using my Health Savings Account), and got a baseline number to work with then. I immediately halted all vitamin D supplementation after the test and instead of pills, I would only receive vitamin D from the sun and whatever foods may have vitamin D (not many that I eat). I did not change my diet in anyway to consciously add any vitamin D via nutrition.
Per most recommendations, based on my location and skin type, I would only need about 10-20 minutes of sun exposure during prime hours (from 10am-2pm) a few times a week with about 25% of my skin showing. These recommendations vary based on the time of year and the time of day (Sunshine Calendar – GrassrootsHealth). With this information, I became more conscious of the time I spent outside, making sure I had some skin exposed. This took the form of more outdoor walks instead of indoor on the treadmill. The heat and humidity can be unbearable during the summer months where I live, but getting at least 10 minutes a few times a week wasn’t too difficult. During these walks the only parts of my body that were exposed were my legs since I always wore a protective hat and covered my arms. Outside of these walks, I did have additional sun exposure during any daytime activities whether outside all day at the beach (with sunscreen on but per multiple studies, sunscreen use still allows vitamin D production Benefits and Risks of Sun Exposure to Maintain Adequate Vitamin D Levels – PMC) or normal tasks like walking to the car, etc.
And what were the results of this mini self-experiment? My beginning vitamin D level with supplementation was 69. Six months later, with no supplementation and only the sun, my level was 37, which is a substantial drop (screenshots below). The range on the vitamin D test states the Reference Range is 30-100 ng/ml so both of my tests fell within those numbers.
What is my optimal vitamin D level?
Now that I knew that I was definitely not deficient and the pills were having an affect on me (since my numbers dropped without them) I wanted to know what was the optimal level. The entire purpose of me paying for the blood tests and doing mini self-experiments with sun exposure instead of pills was to discover what was healthiest and aim for that goal. I didn’t feel any different with or without the pills so I couldn’t use that as a measure for success, but since my levels dropped over twenty points without supplementation, should I begin taking the pills again or was vitamin D synthesis from the sun sufficient? To answer this question, I needed to know what was the ideal number for a light-skinned woman in her 40s, but soon found out that’s not an easy question to answer.
From everything I’ve read, there isn’t an agreed-upon “optimal” range for vitamin D. The experts have gone back and forth and the only thing I can find that’s in stone is that being too low in vitamin D is almost always worse than being too high, but what is too low and what is too high is still up for debate.
Per an article published in 2020, some experts suggested we are over supplementing. In 2010 it was recommended anything above 20 was adequate but a year later the Endocrine Society recommended a level of at least 30 and to “to guarantee sufficiency, we recommend between 40 and 60 ng/mL for both children and adults.” But not long later, some of those same experts stated that levels at 12.5 and below are considered deficient and 20 “was never intended to be used to define vitamin D deficiency.” Vitamin D: What’s the “right” level? – Harvard Health
In a separate article from the NIH published in April 2025, a meta-analysis of 47 papers regarding vitamin D was done and the results of these different studies were summarized. I read through the summaries in the Table provided and the ranges were still quite varied.
Some of the summaries and conclusions are stated below:
“The lowest risk for most of the different outcomes was found at 25(OH)D levels between approximately 40–50 nmol/L and 100 nmol/L (Table 1), with about half of the analyzed outcomes showing the lowest risk at ≤75 nmol/L. Only a few had a lowest risk estimation higher than 100 nmol/L.” The Optimal Protective 25-Hydroxyvitamin D Level for Different Health Outcomes in Adults: A Brief Summary of Dose–Response Meta-Analyses – PMC
“In conclusion, to define a universal level that could be considered optimal for minimizing overall risks, considering the linear and nonlinear outcome relationships of multiple endpoints, is rather a challenge, and it is not possible to determine a common optimal concentration that minimizes the risk for all of these outcomes. All in all, the optimal vitamin D status seems to be tissue-dependent and might also vary by age and race, which would make it difficult to set generally applicable optimal values.”
I appreciate the authors digging through the data, yet an answer is still not agreed upon at this time. Based on their quoted conclusion, I plan to aim for 40-50. I’m currently slightly under that but aim to fix that and If I exceed 50 via the sun only, I see no cause for concern.
Conclusion
My personal thought is that humans are designed to obtain their vitamin D from the sun and food. This is an obvious thought since we are designed to prosper within our natural environment and diet, and supplementation wasn’t started until around 100 years ago. However, our lives are much different then our ancestors so our current way of living tends to keep us more indoors and more clothed. Therefore, careful thought on which foods we choose and how much time spent in the sun and when need to factored in if one chooses not to supplement.
I believe spending time outdoors in the sun is healthy both physically and mentally, but I do want to balance my physical need for sunlight with my desire to avoid premature aging since the sun has been shown to cause up to 90% of visible skin aging How Sun Exposure Accelerates Skin Aging and Ways to Prevent It – Center for Dermatology and lower my risk for melanoma. To accomplish this, I spend as much time in the sun as I desire while at the same time covering my face with either sunscreen or clothing (or both) and doing the same with other parts of my body that were neglected in my youth and already have signs of photoaging, such as my lower arms and chest, to prevent additional damage. My legs and hands also have sun damage but I have no desire to wear gloves and my legs are a large organ so I use them to soak up most of the sun’s rays.
Am I going to restart taking vitamin D pills since my levels dropped? Sometimes.
I’m certainly NOT anti-supplement as I consume more than a few daily, but if I can achieve a healthy and desired amount through the sun only then that will be my goal. Therefore, I am going to continue using the sun for most of my vitamin D needs and only supplement once or twice a week for the time being and retest my levels again later this year. If they continue to fall below 30nl then I will add back in the pills on a regular schedule.
Some of the reasons for trying to obtain the majority of my vitamin D without supplementation is that supplement brands don’t always match what’s stated on the label or they can contain additional ingredients that I didn’t sign up for Some Vitamin D Supplements Contain Much More Than Claimed – ConsumerLab.com, I can’t overdose on vitamin D from the sun, it seems plausible that the sun’s rays are overall beneficial when in correct dosages Effects of Near-Infrared Light on Well-Being and Health in Human Subjects with Mild Sleep-Related Complaints: A Double-Blind, Randomized, Placebo-Controlled Study – PubMed, and there’s some evidence that supplementation does not protect against diseases but UV exposure does Benefits and Risks of Sun Exposure to Maintain Adequate Vitamin D Levels – PMC.
It sounds counterintuitive but it may actually be easier for me to naturally synthesize vitamin D via the sun’s UVB rays in the winter months better than the summer simply because it can be obnoxiously hot in the summer months compared to winter. A part of me is also curious what my ideal vitamin D level should be. My thought is my optimal level should be what the sun can provide for me as long as I provide it enough skin and time to do its work.
Interesting things from studies I learned while researching vitamin D
- “Studies confirm that living closer to the equator lowers the risk of internal organ cancer death. Benefits and Risks of Sun Exposure to Maintain Adequate Vitamin D Levels – PMC
- “To determine the influence vitamin D may have on the prognosis of patients with melanoma, out of 87 patients with malignant melanoma who were observed in a study, only 11 patients (12.7%) demonstrated normal serum vitamin D levels regardless of the anatomical location of the melanoma. Thus, it is hypothesized that vitamin D levels protect against melanoma.” Benefits and Risks of Sun Exposure to Maintain Adequate Vitamin D Levels – PMC
- “Low levels of vitamin D result in higher mortality and disease, and there is an inverse relationship between levels of vitamin D and cardiovascular events and cancer. Supplementation was not indicated to protect against these diseases indicating endogenous vitamin D from UV exposure is the most efficacious protection method. Further studies by Garland et al. indicate that there are twice as many age-adjusted death rates when vitamin D levels are below 22 nmol/L as compared to levels greater than 125 nmol/L. Lindqvist et al. demonstrated that sun avoidance and smoking were of the equal magnitude of risk. Growing evidence shows lower rates of cardiovascular disease and blood pressure incidence with higher sunlight exposure [20].” Benefits and Risks of Sun Exposure to Maintain Adequate Vitamin D Levels – PMC
- “Exogenous and endogenous vitamin D are both beneficial to health. Limited food products are vitamin D fortified, which makes adequate amounts of vitamin D difficult to obtain through diet alone. In one study, only 5% of the body’s skin surface was needed to produce adequate amounts of vitamin D. The backs of the hands and face account for greater than 5% of the body’s surface area. Many sun protection campaigns facilitate the idea of limiting sun exposure to less than 15 minutes per day; however, a study in Boston indicates a light-skinned individual will achieve maximum vitamin D production within five minutes. The rest of the time spent outdoors leads to UV-induced skin damage [6].” Benefits and Risks of Sun Exposure to Maintain Adequate Vitamin D Levels – PMC
- “Studies examining proper 25(OH)D levels indicate there may not be a relative “normal.” Before modern civilization, humans spent much of their time outdoors soaking in UV radiation with no commercial sunscreen. It has been suggested that a baseline for proper serum vitamin D amounts should be compared to lifeguards. Their average serum 25(OH)D was 161 nmol/L, whereas the general population was 68.3 nmol/L. However, lifeguards in the study with 25(OH)D levels at 148 nmol/L exhibited hypercalciuria indicating hypervitaminosis D. A safer level to strive for was suggested to be 140 nmol/L [6].” Benefits and Risks of Sun Exposure to Maintain Adequate Vitamin D Levels – PMC
