How to choose a good vitamin D

A good vitamin D supplement names its form (D3 cholecalciferol or D2), prints the amount in both mcg and IU, stays well under the 100 mcg (4,000 IU) adult upper limit, lists every other ingredient, and shows who tests it. Price per serving is the fair way to compare. Here is the checklist, with our own label measured against it.

1. The form: D3 or D2

Both are vitamin D. A 2012 meta-analysis of randomised trials found D3 raised blood 25-hydroxyvitamin D more than D2 overall, but the advantage disappeared with daily dosing, which is how most people take it. So the form matters less than the next checks. Pick either, and read the ingredient line to see which you have; it should say "vitamin D3 (as cholecalciferol)" or "vitamin D2 (ergocalciferol)". See what is vitamin D for the basics.

Ours: vitamin D3 as cholecalciferol.

2. The amount, in the units that matter

Look for mcg and IU together (1 mcg = 40 IU) and for the percent Daily Value against 20 mcg. The Daily Value is a labeling reference, not a limit. The limit that matters is the adult upper limit of 100 mcg (4,000 IU) a day from all sources. Be wary of a bottle where the serving is more than one softgel, and of "mg" figures for vitamin D, which are almost always a unit mix-up.

Ours: 50 mcg (2,000 IU) per softgel, 250% DV, half the upper limit. One softgel is one serving.

3. The dose against the research

Higher is not better. The largest trial of vitamin D3 at 2,000 IU a day (VITAL, about 25,000 US adults aged 50 and over, median 5.3 years) found no difference from placebo in cancer, cardiovascular events, fractures or depression. In a three-year trial, 4,000 and 10,000 IU a day produced lower radial bone density than 400 IU. We make no benefit claim for any dose; the evidence is laid out in vitamin D benefits: what the research does and doesn't show. Be sceptical of any label that promises bone, heart, immune or mood results: our reading of the trials is that they do not support it for healthy adults.

Where we fall short: we have no dose-matched trial showing a benefit at 2,000 IU, and we do not pretend to.

4. How it is delivered

Vitamin D is fat-soluble. A trial of 50 adults found a single dose absorbed about 32% better with a fat-containing breakfast than a fat-free one, so the meal you take it with matters (see when is the best time to take vitamin D). We found no trial we can cite that compares softgels with tablets, gummies or drops for absorption, so we do not rank them. Softgels carry oil; tablets and gummies carry other fillers.

Ours: a softgel in soybean and corn oil.

5. Other ingredients and what you avoid

Read the other-ingredients line. Check for allergens (soy, corn), animal-derived gelatin or lanolin, sweeteners, and colours. Vegan products exist; they use a plant-based capsule, and a D3 or D2 that is not animal-derived.

Ours: softgel (gelatin, glycerin, water), soybean oil, corn oil. It is not vegan or vegetarian, and it contains soy and corn oils. The label does not state the animal source of the gelatin or of the vitamin D3, and we have not confirmed either.

6. Testing: what can and cannot be verified

Label accuracy is a real issue for oils and softgels. In a 2011 Italian analysis, a cod-liver-oil supplement taken by three people diagnosed with vitamin D3 intoxication contained about three orders of magnitude more vitamin D3 than its label declared; other batches of the same product matched the label. That is a single case, not a rate, but it is the reason to look for independent testing. Look for a certificate of analysis or an independent testing mark that you can verify with the program that issues it.

Where we fall short: we do not currently hold a third-party certificate of analysis for this product that we can show you, so we make no testing claim.

7. Price per serving

Divide the price by the number of servings, not by the bottle count, and check that a serving is one softgel. Electric Tiger Vitamin D3 is 100 softgels a bottle, as low as $15.35 a bottle on a 3-bottle subscription, or about $0.15 a serving. That is our subscription price against a listed single-bottle price elsewhere, so compare like with like.

Questions people ask

Which vitamin D3 supplement should I pick, and is there a top brand?

We do not rank brands. The right one for you passes the checks above: named form, clear amount under the upper limit, plain ingredients, evidence of testing and a fair price per serving. Ours names its form, prints the amount in mcg and IU under the upper limit and gives a price per serving; it falls short on testing evidence, and it is not vegan.

Where can I get vitamin D3, and where to buy it?

Vitamin D comes from skin exposure to sunlight, some foods (fatty fish, egg yolk, fortified foods) and supplements. Supplements are sold in pharmacies, grocery stores and online, and from us.

How should I take vitamin D3, and when?

With a meal that contains fat. See when is the best time to take vitamin D.

Which is best, liquid drops or capsules?

We found no trial we can cite comparing the two for absorption or outcomes, so we do not rank them. Pick on the checklist and on what you will take daily.

Is there a vegan vitamin D3?

Yes, from other makers. Ours is not vegan: the capsule is gelatin.

Which vitamin D3 supports bone health, and what are the top-rated ones?

We make no bone-health claim for any vitamin D dose: the trials above did not show an effect on fractures or bone density. Be careful with "top-rated" lists. We cannot verify them and do not publish one.

Which vitamin D3 absorbs most easily, and who offers a subscription?

Bioavailability: no trial we can cite ranks products, and the form and fat studies above are the evidence there is. Subscription: we sell one, as low as $15.35 a bottle on a 3-bottle subscription.