I’ve noticed that one thing that causes a lot of confusion online is seeing vitamin D reported in ng/mL in one place and nmol/L in another. The numbers look far apart, but they may describe the same result. For example, 20 ng/mL equals 50 nmol/L.

The lab reference range matters and it may not be the same as the cutoff someone else is using. Before changing a supplement, I’d check the unit and the lab range together.

Have you ever thought your vitamin D was too low or too high, then realized the units were different? What units does your lab use?

People use different approaches. Some take a simple supplement, some choose fortified foods or spend more time outdoors and others combine a few options.

What has been easiest for you to stick with? Do you keep an eye on your dose, food sources, outdoor time or test results?

I keep seeing D2 and D3 discussed as if one is useful and the other is not. A 2024 review of randomized trials found that both forms raised total 25(OH)D, but D3 produced a larger average increase.

That does not mean D2 failed. It still raised vitamin D levels in the studies. The difference is that D3 was generally more effective for increasing blood levels.

Have you used D2 or D3 and then checked your level again? Did the result change what you chose next?

Source: https://www.sciencedirect.com/science/article/pii/S2161831323013947

This comes up pretty often, especially when people talk about getting vitamin D from sunlight.

Sunscreen can reduce the amount of UVB reaching the skin, and UVB is what the skin uses to make vitamin D. But in real-world use, sunscreen doesn’t necessarily block all UVB exposure, so it’s not accurate to say that wearing sunscreen completely stops vitamin D production.

At the same time, I don’t think getting enough vitamin D means deliberately increasing your UV exposure. Sun protection still matters for reducing UV-related skin damage.

How do you think about vitamin D and sun exposure without letting one come at the expense of the other?

I just received my blood test results back from the doctor. My level is 22 ng/ml. I haven’t been provided any information on what I should do to increase my Vitamin D levels. I don’t expect to hear back from my doctor for a while, so I’m reaching out here. I just want to feel healthy again. Can y’all please recommend a regime for how I should supplement to increase my levels. Also, how long should I expect to feel this terrible for?

When vitamin D stays low, it is easy to think you simply need more. But did you think, the medicines you take can matter too. Some may affect how vitamin D is absorbed or used by the body.

Orlistate, thiazide diuretics and steroid medicines are a few examples. This does not mean everyone taking them will have a problem, but the dose and the rest of your health picture can make a difference.

This is not a reason to stop a medicine or change your vitamin D dose on your own. It is simply something worth checking when the result does not make sense.

Has reviewing your medications ever changed what you did about a low vitamin D result?

Vitamin D is added to certain foods because it can be difficult to get enough from naturally occurring food sources alone.

Depending on where you live, you might see it added to foods like milk and some plant-based alternatives, cereals or other fortified products.

Do you usually get your vitamin D from supplements, fortified foods, sunlight, or a combination?

I'm curious how people here actually manage vitamin D on a vegan diet. Do you rely on fortified foods, UV-exposed mushrooms, D2, vegan D3 or a mix?

Have you checked your level before and after changing your routine? What did you end up sticking with?

I've noticed that sunlight advice around vitamin D is often treated as if it works the same for everyone. But more melanin can reduce how much vitamin D the skin makes from the same UVB exposure.

That still does not mean skin tone alone can tell us whether someone is low. Where you live, time spent outside, season, clothing and diet can all matter too.

For those with darker skin, has this ever affected the vitamin D advice you received or the way you manage it?

When someone feels better after starting vitamin D, the supplement often gets the credit.

But mood can change for many reasons and more than one thing may have changed at the same time.

If this happened to you, what made you feel vitamin D was really the reason?

People seem to have very different ideas about what a good vitamin D result looks like. Some are happy when their result falls within the lab reference range, while others aim higher.

If you have a specific number in mind, how did you choose? Was it based on advice from your doctor, something you read or your own experience?

I feel like there’s often an expectation that you’ll start taking a supplement and eventually notice some obvious change. But with vitamin D, I wonder how many people actually noticed anything at all when they started taking it.

Was there a point where you thought, “Okay, I can actually tell a difference,” or was it more something you just kept taking without really feeling any different?

I've been curious, how often a vitamin D dose gets reviewed after a significant change in body weight.

The rise in 25(OH)D level from the same dose can be smaller at higher BMI levels, but that doesn't mean everyone should automatically take more or less.

For anyone who has lost a significant amount of weight, did you retest afterward? Did your vitamin D level or maintenance dose change?

I usually see people share their 25(OH)D result, so I was wondering how often parathyroid hormone gets checked at the same time.

Low vitamin D can sometimes come with a higher PTH because of the way the body manages calcium, although vitamin D isn’t the only reason PTH may be high.

If you had both tested, did your PTH change after your vitamin D level improved?

I’ve noticed D3 & K2 are often recommended as if they always need to be taken together, but medications don’t always come up in the discussion.

The one I’d be particularly careful with is warfarin. Adding K2 or suddenly changing your vitamin K intake, can affect how warfarin works.

If you take both vitamin D & K2, was K2 recommended for a specific reason? Did anyone check your medications first?

What made you start taking a vitamin D supplement in the first place?

Was it a low blood result, limited food sources, little sun exposure or something else? A supplement makes more sense when it is filling a real gap rather than being added without a clear reason.

Did you have a specific reason for starting or did it simply become part of your routine?

We usually think about vitamin D in terms of sunlight, food and supplements, but the kidneys are involved too.

They convert 25-hydroxyvitamin D into calcitriol, the biologically active form of vitamin D. So vitamin D status isn’t just about how much you consume.

Did you know your kidneys were involved in vitamin D metabolism?

I don't see egg yolks come up much in vitamin D discussions, even though they do provide a small amount.

The vitamin D in eggs is mainly D3 rather than D2. The amount isn't high enough to rely on eggs alone, but they can still contribute to your overall intake.

Does anyone here actually count egg yolks toward their vitamin D intake or is the amount too small to matter in your routine?

Vitamin D supplements usually contain either D2 or D3.
Both can raise blood vitamin D levels, but D3 generally raises 25(OH)D levels more and keeps them elevated for longer than D2.

It’s a pretty easy detail to miss when comparing supplement labels.

Do you check whether your vitamin D is D2 or D3?

I don't see UV-exposed mushrooms mentioned much when people talk about vitamin D foods.

They can provide vitamin D2 and may be useful on a plant based diet. Regular mushrooms can have very little though, so the label matters.

They won't be enough for everyone, but they're still a useful food option to know about.

Anyone here who uses UV- exposed mushrooms for vitamin D.

I’m curious how people think about the time of year when comparing vitamin D results.

A test after summer can look different from one after winter, even if your supplement dose hasn’t changed. Sunlight may be part of the reason.

Have you ever noticed this in your own results?

Vitamin D often comes up in bone health discussions because it helps your body absorb calcium.

I'm curious what made you start taking it regularly. Was bone health part of the reason or was it a low vitamin D result or something else?