DIY vitamin d blog post featured image

Worried about Vitamin D deficiency or seasonal affective disorder? Looking for a cheaper alternative to the Sperti sun lamp?

In this guide, I’ll walk you through step by step how to build your own vitamin D lamp!

Since this setup also emits UVA, it can also function as a tanning lamp for those of you looking for that.

Why Did I Build This?

I live in Michigan, so for several months of the year, the sun is too low for vitamin D production.

Why not use the Sperti lamp? Well, this DIY lamp is cheaper, more powerful, and safer.

Explaining the UVB to UVI Ratio

You see, reptile owners have done a lot of UVB light testing. And they’ve discovered a simple metric to determine how safe a UVB light source is.

This is the UVB:UVI ratio.

It’s a proxy measurement, but it’s a very useful one.

This ratio tells us roughly how much short-wavelength radiation is present in a light source, without using a $3,000 UV spectrometer (which I don’t have). Please Santa.

Here’s how we figure this out:

At a set distance, say two feet, you measure the UV index and the total UVB in uW/cm2.

uv meter measurement ranges compared to sunlight
UV meter measurement ranges relative to natural sunlight

As you can see above, the UVB meter detects longer wavelength light than the UVI meter.

If we get a UV index reading of 14 and a total UVB reading of 200 this gives us a ratio of 14.3, while if our total measured UVB was 350 at the same UV index, the ratio would be 25.

A lower ratio is indicative of there being more short-wavelength UVB than long-wavelength.

This is bad because natural sunlight doesn’t go much past 300nm, while lamps like the Sperti go down well into the 250-270nm range.

Here are the average UVB to UVI ratios for the Sperti lamp vs the DIY light I built:

  • Sperti: 10.3
  • DIY: 25.7

As you can see, the Sperti lamp is producing far more short-wavelength UVB light than our DIY lamp.

So in other words, at a UVI of 14 (where you are recommended to use the Sperti), both lamps have a drastically different amount of UVB.

  • Sperti UVB at UVI of 14: 130 uW/cm2
  • DIY UVB at UVI of 14: 360 uW/cm2

So you’re able to get exposed to almost 3x more UVB radiation at the same UV index. This is because the Sperti lamp is pushing out more short wavelength UVB, which is sending that UVI up.

It’s unclear if the DIY light will be more effective, but it’s likely that it will be, on top of that, because it has significantly less short wavelength UVB radiation, it will be a lot safer to use long-term.

Hopefully that all made sense.

Let’s build this thing!

The Parts You’ll Need to Build it

First, let’s go over the parts we’ll want to pick up to build our lamp.

Fluorescent UVB Lights

The most important part of this build is of course the lights. For these, I went with the 46″ Dragon D3 made by Arcadia.

I’ve selected this light because it has the highest output UVB I could find and Arcadia makes some really high-quality stuff.

They’re also quite large at 4 feet so we’ll be able to cover far more surface area than the Sperti lamp.

Arcadia 46″ 14% UVB Bulbs

ad14 4654 240

You’ll need four of these total to fill up the light fixture below.

ReptiSun 46″ 10% UVB Bulbs

51IS6nleuLL. AC SL1500

Here’s an alternative that can be purchased on Amazon if that’s more your style.

Note: I didn’t test these in my setup, but they should work just fine, ZooMed is a reputable brand.

Grow Light Fixture

The fixture we’ll be using is a 4-foot grow light fixture. This is explicitly built for 54w fluorescent T5-HO bulbs, the same ones we’ll be putting in it.

4ft T5 Grow Light Fixture

51Q5w2XMdIL. AC SL1500

You don’t have to fill this whole thing if you don’t want to, you could just use two bulbs instead of all four.

It does come with 4 bulbs of its own that we won’t need, so you can recycle those if you want. I’ve been unable to find a fixture that doesn’t come included with lights.

The Protective Screen

The one possible downside to this setup is that it doesn’t come with a protective grate, which is nice to have because fluorescent UVB bulbs utilize mercury. You don’t want to break these bulbs.

If you live alone and aren’t worried about anyone breaking it, you can always skip this part.

The best option I’ve been able to come up with is attaching a metal wire mesh to the front.

916DibINSbL. AC SL1500

1/2 Inch Galvanized Welded Wire Mesh

This mesh is quite stiff and will work well to protect the lights.

61V7SsLA5eS. AC SL1200

Adhesive Zip Tie Mounts

You’ll need something like this to attach the mesh to the light fixture.

Building the Vitamin D Lamp

Okay, now let’s put it all together!

Preparing the Light Fixture

Here’s what you’ll need to do with the fixture.

  1. Remove the blue protective film from the reflective trays, this is pretty easy.
  2. Play around with fitting the trays into each other, they come a bit loose but once you play around with them for a bit you’ll figure out how they fit together.
  3. Clean up any smudges.

Installing the Bulbs

Now carefully pull the bulbs out and install them one by one, these are bi-pin lights, so the connectors on either side install vertically into the fixture.

You may have to push the light fixture connecter out on one end to get the light pins to fit into the slot.

Once it’s sitting in the slot on both ends and is pushed down all the way, you can spin it to the right to lock the light into place.

Now repeat for all four lights!

Mounting it on the Wall

To mount the light on your wall of choice, you’ll want to start by installing a hook or screw of some kind into a stud at around 70″ off the floor.

Next, you’ll hang the light using one of the hooks it came with.

closeup image showing hook attachment to screw in stud
Just like that! Don’t mind the crack in the wall, it’s not that heavy, that’s just my amazing drywall work.

I also went ahead and attached the bottom to the wall using a couple of 3M sticky pads.

Here’s what the finished product will look like:

the diy vitamin d lamp fully installed on the wall

Not bad!

Installing the Protective Grate

Now for the protective grate, should you want it…

You’ll need tin snips for this part!

Cut off a 49″ long section of the mesh, and begin to make it flat so it’s easier to work with.

Next, place the mesh against the panel and start bending the top portion over, it’s pretty stiff and tough mesh so this isn’t the most effortless process.

Once you have the top done, you can move on to the sides.

The trick here is to bend the sides just a bit, near the top, so that you know where it will need to be bent all the way down.

Once you have a reference point, take the mesh off and bring it over to a flat surface with an edge (like a table or counter) and bend the mesh all the way down on both sides using that edge, it’s much easier this way than trying to do it on the lamp.

  • Tip

Make your bends just a bit more than 90 degrees, this way once it’s attached to the light, the metal won’t want to pull away from the zip-tie mounts.

Once it’s all bent to shape, you can cut out the corner sections that aren’t needed.

closeup view demonstrating the cut corners of the mesh
Example of how the corners will look once you’ve cut them to shape.

And that’s about it! It’s a little bit of a pain, but once it’s done it’s done.

Just stick your zip tie mounts onto the light and start zipping the mesh into place!

Testing the DIY Light

I used the UVA, UVB, UVC, and UVI meters from Solarmeter to test this light setup.

As soon as I began, I realized it was going to be a little challenging, because, unlike the Sperti lamp, this one ramps up to its max within the first 2-3 minutes (if it’s warm).

the uv index over time at 25 inches from light
UV Index @ 25″ over a 15-minute time span

As you can see, it then slowly comes down to baseline over the next 15 minutes or so.

It’s a bit harder to compare the two because of this.

But I tried anyways.

UV Index Measurements

As you can see from the graph below, this DIY lamp is quite a bit more powerful than the Sperti lamp:

sperti uvi vs diy uvi bar graph
UV Index of Sperti lamp vs DIY lamp

This means that while you get a UVI of 14.3 at 15″ from the Sperti, the same UVI is reached at 24″ for this light.

If you’d like to take a deeper dive into the measurements for this light as well as the Sperti, the google sheets document can be found here.

  • Learn more

You can read our review of the Sperti vitamin D lamp here if you’re interested.

UVA Measurements

Since the UVI pretty much only takes into account UVB and lower, what about UVA?

Well, the DIY light puts out way more UVA than the Sperti light does.

bar graph of uva from sperti lamp vs uva from diy lamp
It produces boatloads more UVA than the Sperti lamp

Is this a good thing or a bad thing though?

Well, natural sunlight does produce quite a bit more UVA than UVB, so this seems to mimic sunlight in that regard better than the Sperti.

Of course, this can also double as a tanning lamp as well if you spend more time in front of it.

You may not want this much UVA, perhaps you’re only interested in the UVB aspect, if that’s the case you’ll want to skip this. I’ll see if I can create an affordable narrowband UVB light in the future.

Does UVA Affect Vitamin D Production?

Kind of.

In this study, in which 75 participants total finished. The researchers compared vitamin D production in 4 groups.

UVB only, UVA only, UVB+UVA, and a control.

It was observed that almost no differences were seen in the full spectrum UVA+UVB group when compared to the UVB-only group.

uva and uvb vitamin d study screenshot

In fact, the full spectrum group actually had a higher mean change in serum D3 than UVB only.

They do note that under longer duration times (≥9 min) UVA may decrease pre-vitamin D3 production. Which is fine, UVA does act as a D3 modulator in nature.

So I don’t think there’s anything to worry about here. In fact, it’s likely a good thing as UVA is useful for nitric oxide production, blood flow, and increasing endorphins.

How to Use Your Vitamin D Lamp

Okay, so it’s built, mounted, and you’re ready to stand naked in front of it.

But how far away? And for how long?

The Warm-up Period

If you use this sporadically, the lights do take a few minutes to warm up.

So if you don’t use it often just give it 5 minutes to warm up first. Once the lights are all shining uniformly it’s good to go, you’ll see what I mean.

However, if you use it every day or every other day, they warm up very quickly.

How Far Away Should You Stand

I recommend placing a piece of tape on the floor about 26″ away from the wall.

This is about where you should stand.

  • Tip

Grab a pair of UV glasses before using this!

The metal mesh grate decreases the UV output by about 10-15%.

If you have the protective grate on, stand on the tape.

If you aren’t using the grate, stand behind the tape.

This will give you a UV index of about 14, just like the Sperti does.

How Long Should You Use the Light

How you react to ultraviolet radiation depends on your personal situation.

Depending on your skin type, diet, genetics, and all the rest, the time to erythema will vary.

Erythema is, for those that don’t know, just reddening of the skin. If your skin is getting very red, you’re standing too close for too long.

Simple as that.

Didn’t get red at all? Feel free to increase the time or stand a little closer. Just only change one variable at a time so you know what is and isn’t working for you.

The Best Time for UV Exposure

The best time to use this would be in the middle of the day, preferably after some infrared exposure. As infrared is protective against UV damage.

For most, the best routine would be to use some kind of infrared light therapy in the morning, followed by a UV light session when they get home from work.

You don’t really want to expose your skin to UV first thing in the morning because it’s just very unnatural. I would think this might have a negative effect on your skin and potentially cause problems with circadian timing and hormone rhythmicity.

Alright, that’s it!


I’ve personally used the Sperti and I can confidently say that my DIY sun lamp feels much better.

It feels warm and powerful like the sunlight I’m so fond of standing underneath when I can.

Hopefully, this has inspired you to build your own!

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  1. Hey Derek, thinking about building my own – would the 22″ bulbs and matching enclosure be pretty much the same process and specs, if I wanted something smaller like the sperti for primarily torso/back exposure? Do you think it would be a bit risky to use this set up without testing with all the UVA/B/C meters or pretty safe since it’s from a reputable brand (Arcadia)? Thanks for the write up, it’s very illuminating.

  2. Hey Derek – thanks so much for this, brilliant as ever. I agree its much cheaper than my Sperti d lamp and more powerful obviously and a larger surface area for tanning means less time and more comfort. The only thing bothering me is the UVB/UVA mix. I am not sure I want a higher UVA content, it’s unclear to me whether this is an advantage or not. It more closely resembles natural sunlight for sure, but its not full spectrum either so uncertain if this is a benefit. UVA rays do not contribute to vitamin D production, its clear that stops at around 310nm, but they do contribute to skin damage and possibly malignancy as the rays travel much deeper into the skin. I am not interested in getting a tan, so really want to maximise the UVB benefits of D production in the skin. After 30plus years of observations, I am certain that D3 from a bottle is nothing like D3 made in the skin.
    I am only 1 week into the Sperti but will update my results here after a month or so. I won’t be relying too much on the test levels as supplementing with 10K of D3 for many months raised my levels to high but did precisely nothing for my health and well-being I will be going on symptoms being relieved and my well being. That is obviously much more important to me than numbers on a sheet.
    My observations so far with the Sperti are that 3-5 mins every other day does seem maybe to be too little – I am maintaining a clear limit at 15inches. I will do 5mins a day back and front for a while and then hopefully switch to a maintenance programme of hopefully 5mins every other day. I know I am still very deficient so need a kind of loading dose to catch up.
    BTW the link to the fitting fixture says no longer available. However you can buy the desert lamps with the full kit, you get a fitting with each tube obviously but it still works out way way cheaper than a Sperti and you could choose to use 3 tubes only say and still get the much improved coverage. Hope this helps someone.

    1. Good to see you read it Tom!

      I hear you on the UV ratio, it was something I was unsure of at first, but I’m quite happy with it. While it’s true that UVA doesn’t contribute much to vitamin D, it does contribute to nitric oxide production, as well as endorphin release.

      I can say with absolute certainty that this lamp feels more like genuine sunlight and I have a feeling that’s from the endorphins.

      In this study, they took 14 UV bed users, and had them use tanning beds with UV light and with UV light filtered out. The heat was kept similar, just the UV was filtered out, so blinding was in effect.

      The beds UV spectrum was 4% UVB and 96% UVA, so quite a bit more UVA than our DIY light above.

      Even though the beds they were using were blinded, they still chose to continue using the bed with UV. Showing that UVA was producing a noticeable positive effect in these users.

      Very interesting if you ask me!

      So yes if you’re only interested in vitamin D production, narrowband UVB will do that better than a fuller spectrum light source like the one used here.

      However, I’m of the mindset that there are copious benefits to full spectrum UV beyond just vitamin D.

      1. “However, I’m of the mindset that there are copious benefits to full spectrum UV beyond just vitamin D.”
        I am without doubt you are right – that boost you get from a summer hol by the sea is unbeatable and vitamin d is just a part of that. I suspect sea bathing is infusing your body with minerals that go straight to the bloodstream transdermally I also suspect that UV light oxygenates your blood and ozone is involved too. Probably as you say a whole bunch of things going on. I will give the Sperti light 60 days and then I may make the Desert T5 version myself.

          1. Negative ions, ozone, transdermal minerals – lots to talk about – cant wait – this is true health.

        1. I notice too you cite this book

          The Ultimate Guide To Red Light Therapy: How to Use Red and Near-Infrared Light Therapy for Anti-Aging, Fat Loss, Muscle Gain, Performance Enhancement, and Brain Optimization

          A while ago I built a red light therapy device with a mixture of 1w leds in the 660-850nm range. I am wondering if you have experimented with this wavelength of light and if so what benefits you noted. The commercial offerings seem very very expensive for what is essentially a box with a bunch of LEDs and a fan. They of course claim almost miraculous powers however.
          Of course this wavelength of light is a big part of sunlight and may help to explain some of the benefits of real sunshine and maybe how this part of the spectrum prepares the body for UV light later in the day. Its all very fascinating for sure and a much more complex picture than most would understand I guess.

          1. I couldn’t agree more. I haven’t played around with wavelength specific IR therapy myself yet, as you said it’s very cost prohibitive.

            I have used incandescent infrared, much of this peaks in the IRA range so it contains a lot of beneficial infrared radiation for relatively little cost.

            However, the one downside to blackbody infrared is that it also puts off quite a bit of IRB and IRC. Since natural sunlight is filtered through the atmosphere, water vapor actually absorbed a lot of this.

            So sunlight is quite heavy in IRA and quite low in IRB and IRC.

            You can mimic this water filtered infrared phenomenon by simply shining incandescent light through water! This is called wIRA and is actually used medically, however there are no real viable commercial devices.

            I’m still trying to figure out an easy way to create one, as I think it would be the ideal infrared therapy device.

        1. Yeah it is, that’s why I ended up making my own 😅

          So for that bulb it would depend on the fixture or reflector used. It would work though, can’t say how well or anything, but yeah you’d make vitamin D No doubt about that.

          Really wish companies would provide better information. The product box likely shows UVI at various distances, but hard to say without knowing that.