The Best Vitamin D Supplement

To find our top picks, we consulted doctors and nutritionists from across the country, read through hundreds of ingredients labels, and utilized the results from three different independent lab tests. In the end, we found two supplements that stand the best chance of boosting your vitamin D levels.

Best Value Pick
Kirkland Signature Extra Strength Vitamin D3 2000 IU
Kirkland Signature
Includes everything you could want in a vitamin D supplement — and nothing you don’t — for the lowest price.
Pros
Few ingredients
Great value
Cons
Requires a membership (for savings)

Why we chose it

Few ingredients

We liked the short list of ingredients: 2,000 IU of vitamin D3 (as cholecalciferol, which mimics the way the body naturally processes vitamin D), soybean oil (rich in heart-healthy polyunsaturated fats), plus gelatin, glycerin, and water for the softgel capsule. Kirkland Signature even earned kudos from not one, but two independent labs. Its label bears the USP symbol, arguably the gold standard for product testing. USP certification is recognized around the world.

Great value

At about $0.01 per serving, it’s less than half the cost of our other top pick. We loved the Costco-sized bottle, which contained 600 softgels that were as small as any we tested. After all, if you’re going to make vitamin D supplements a part of your daily routine, you might as well make it easy on yourself: one tiny pill that’s easy to swallow, in a bottle that will last for a good 20 months. At $3.50 per year, Kirkland Signature Extra Strength Vitamin D3 is an inexpensive way to stay up on your vitamin D intake.

Points to consider

Requires a membership

If you prefer to purchase your vitamin supplements in stores, you may be out of luck. The Kirkland Signature brand is exclusive to Costco, which requires its shoppers to purchase a monthly membership fee. While we did find it available for sale on Amazon, you’ll need the Costco membership for a cheaper price.

Best Drugstore Pick
Nature Made Vitamin D3
Nature Made
A few more cents per serving for nearly identical ingredients, but available in more stores than Kirkland Signature.
Pros
Tested purity
Availability
Cons
Lower dosage

Why we chose it

Tested purity

Nature Made is the only other D3 supplement tested by both USP and Labdoor to ensure purity and potency, plus it includes soybean oil to help boost absorption.

Availability

Unlike Kirkland Signature, this product is available in most brick-and-mortar stores. You can pick your supplement up membership-free while out running errands. You can find it at grocery stores and pharmacies nationwide including Target, Walgreens, and Safeway.

Points to consider

Lower dosage

Nature Made also only contains 1000 IU of vitamin D per pill (half as much as Kirkland Signature). Our experts recommend 2000 IU per day to most of their adult patients. If your doctor agrees, you’ll need to take two pills per day. But the tablets are tiny, and a lower dose does mean you can easily take more or less vitamin D as needed.

Guide to vitamin D

How to make sure you’re getting enough vitamin D

Deficiency is common

An estimated 41% of US adults are vitamin D-deficient, and that has serious long-term effects. “Without vitamin D you won’t absorb calcium in your gut, which leads to an increase in bone loss,” says Dr. Feuerstein. Shuck adds, “Vitamin D also has other key functions in the body, such as helping to maintain normal immune system functioning.”

Get vitamin D in your diet

There are food sources of vitamin D, notes nutritionist Shereen Lehman: “Oily fish like salmon and tuna have some vitamin D, and eggs do as well. Mushrooms like maitake and chanterelle can be a good source, as can portabella mushrooms grown in UV light. Otherwise, look for foods fortified with vitamin D like milk, breakfast cereals, and many brands of nut milk.”

Vitamin D-rich foods
IU per serving
Maitake mushrooms
943
Swordfish (3 oz)
566
Sockeye salmon (3 oz)
447
Chanterelle mushrooms
178
Canned tuna fish (3 oz)
154
Orange juice - vitamin D-fortified (1 cup)
137
Milk (1 cup)
115-124
Egg (1 yolk)
41

But can you get enough D just from food sources? That depends on how hungry you are. The National Institutes of Health (NIH) found that even foods rich in vitamin D require multiple servings to meet the recommended 600 IU per day.

Sunbathe safely?

Some medical researchers, like Dr. Michael Holick, recommend getting 15 minutes of unprotected sunlight per day — in the middle of the day when the sun is brightest. And Dr. Andrew Weil recommends 10 minutes of sun per day. But the American Academy of Dermatology disagrees, and suggests we use skin protection (clothing and sunscreen with an SPF of 30 or higher) every time we’re out in the sun, to prevent skin cancer. So what’s the right answer? We suggest checking with your doctor to find out what’s right for you.

Vitamin D FAQs

How do I know if I’m low on vitamin D?

Many doctors routinely check vitamin D levels during a patient’s annual physical exam. A simple blood test, called the 25(OH)D, will determine the amount of vitamin D stored in your body from all sources, including sun, diet, and supplements. In fact, the test measures stored vitamin D as far back as 15 days, which makes it the ideal way to get an accurate measurement of your vitamin D level. If your doctor doesn’t already check your vitamin D levels during your annual exam, just ask for the test.

Another option: a home testing kit for under $70 from the Vitamin D Council. You prick your finger and place a drop of blood on blotting paper, and then send it to the lab, which will mail you your results.

If your test determines that you’re deficient in vitamin D, Dr. Feuerstein suggests working with your medical provider to determine the best dosage — and getting tested every six months until you reach your goal. He routinely tests his patients twice a year to determine if their vitamin D level changes from summer to winter.

What does vitamin D do for my health?

Scientists have known for years that vitamin D plays a key role in creating and maintaining healthy bones. But as Dr. Feuerstein explains, we’re learning more every day. “We have vitamin D receptors in nearly all the tissues of the body, and we’re learning about its effect on cancer, heart disease, multiple sclerosis, and in autoimmune disease.”

The Mayo Clinic makes a strong case for the far-reaching benefits of vitamin D with a list of 59 medical conditions that are either improved by vitamin D or affected in ways that warrant further study. This list includes thyroid conditions, fibromyalgia, psoriasis, dental cavities, and even Alzheimer’s disease.

The takeaway? Research suggests there are plenty of good reasons beyond maintaining healthy bones to make a vitamin D supplement part of your daily regimen.

Can you get too much vitamin D?

Yes. The Institute of Medicine (IOM) says the average adult should take no more than 4000 IU of Vitamin D per day. The Recommended Daily Allowance for most adults is 600 IU. But the majority of the supplements we looked at contained between 1000 and 2000. Why so much? Our experts suggested that the RDA — which dropped from 2000 IU all the way down to 600 IU in 2010 — might not be enough to prevent a vitamin D deficiency.

But there’s no hard and fast rule — and much of it depends on environmental factors. An office worker in cloudy Seattle will likely need more vitamin D than a lifeguard in Los Angeles, for example. Before you start taking supplements, talk to your doctor about the right dosage for you.

The best vitamin D supplements: Summed up

Kirkland Signature Extra Strength Vitamin D3
Nature Made Vitamin D3
The Best
Value Pick
Drugstore Pick
Price
$12
$15
# of capsules
600
250
USP-verified
Labdoor rating
81.5/100
85.9/100
Vitamin D3 content
2000 IU
1000 IU