Kirkland Signature Extra Strength D3 50 mcg (2,000 IU)

1. Ingredients 25% of the rating 4 of 5

   One active plus soybean oil, porcine gelatin, glycerin and water; no flow agents, colors, sweeteners or fillers, but it is soy and animal-derived.

2. Independent testing 35% of the rating 3 of 5

   USP Verified is on the label and Costco’s page and in USP’s own June 2023 list, which covers label amounts, contaminants and dissolution; but the brand pays for it, no results are published and USP’s live directory blocked us.

3. Evidence 15% of the rating 5 of 5

   A plain D3 softgel at 2,000 IU matches the guideline range and the page claims only bone, teeth, muscle and immune support.

4. Trust 10% of the rating 4 of 5

   We found no supplement recall, FDA warning letter or Prop 65 notice for this product, but the label does not name who makes it.

5. Value 15% of the rating 5 of 5

   $14.99 for 600 softgels is $0.025 a day, the cheapest vitamin D on this list.

The rating, 4.0 of 5, is the weighted average of these scores. See how we rank vitamins & minerals and our standard.

1. Vitamin D3 (cholecalciferol) 50 mcg (2,000 IU)
2. Soybean oil
3. Gelatin (porcine)
4. Glycerin
5. Water

• Paid certification USP Verified (listing seen in USP’s own page, Internet Archive copy of 6 June 2023) June 2023

  USP’s Kirkland Signature page then listed “Vitamin D3 2000 IU Softgels”. Costco’s page and the NIH label record carry the mark. USP says the mark means the ingredients and amounts match the label, specified contaminants such as heavy metals and pesticides are not at harmful levels, the softgel dissolves, and it is made under FDA manufacturing practices. The brand pays for it and USP publishes no results. Open ↗ (opens in a new tab)

Who actually makes it?

The label does not say. NIH’s label record (opens in a new tab) lists only “Distributed by Costco Wholesale Corporation”, so this is a private-label product and we cannot check the maker’s history. The USP mark, if current, covers the manufacturing process, not the name.

Is it really still USP Verified?

Costco’s page and the label say so, and USP’s own page listed it in June 2023 (opens in a new tab). USP’s live directory blocks our tools, so we cannot see today’s listing. We count it as a certification, not as proof.

Has Costco or Kirkland had supplement recalls or Prop 65 notices?

Not that we found. FDA’s enforcement records (opens in a new tab) for Costco list food recalls (salads, pastries) and none for a supplement. Among the 200 most recent California Prop 65 notices (opens in a new tab) matching “Costco Wholesale”, none concerns a vitamin or supplement. We found no FDA warning letter.

Is the softgel suitable for vegetarians, or for people avoiding soy or pork?

No. The shell is porcine gelatin and the fill is soybean oil. Momentous’s capsule uses olive oil and a plant-based shell.

Do vitamin D supplements really contain what the label says?

Not always. A 2013 JAMA Internal Medicine study (opens in a new tab) bought 55 bottles from 12 makers and found 9 to 146 percent of the labeled vitamin D, with the one USP-verified product generally more accurate (summary (opens in a new tab)). This softgel has no published potency result, so its USP mark, if current, is the only check on the dose.

• The label is plain: one active ingredient, vitamin D3 (cholecalciferol) 50 mcg (2,000 IU) per softgel, half the 4,000 IU upper limit for vitamin D and inside the range our supplementation guide prefers. We read it in the NIH Dietary Supplement Label Database, which holds the Kirkland Signature “D3 50 mcg (2000 IU)” label for item 393914, entered in December 2022.
• The other ingredients are named: soybean oil, gelatin (porcine), glycerin and water in the NIH record, and Costco’s page lists soybean oil, gelatin (porcine), glycerin and vitamin D3. There are no flow agents, colors, sweeteners or fillers.
• Costco’s page lists it as “United States Pharmacopeia (USP) Verified”, and the NIH label record carries the seal “USP Verified Dietary Supplement”. USP’s own Kirkland Signature page, in an Internet Archive copy of 6 June 2023, lists “Vitamin D3 2000 IU Softgels” among its verified products.
• It is the lowest cost per day of the vitamin D3 products we list. Costco.com shows $14.99 for 600 softgels (about 2.5 cents a day), and a $2.50 manufacturer’s savings valid through 15 November 2026 brings it to $12.49.

• We could not open the live USP Verified directory (quality-supplements.org returns “Access Denied” to our tools), so today’s status rests on the label, Costco’s page and a three-year-old copy of USP’s list.
• The label names Costco as distributor and does not name the manufacturer, so we cannot look up who makes it or check that maker’s record.
• It is sold in Costco warehouses. Costco.com showed it as unavailable online, and the page says prices vary by warehouse, so the price above is the online listing and a warehouse price may differ.
• The softgel contains soybean oil and porcine gelatin, so it is not for anyone avoiding soy or pork products. No certificate of analysis is public. The NIH label record dates from December 2022 and Costco notes that label information from suppliers may change, so read the bottle you buy.

Tested by

USP Verified (on the label and Costco’s page; listed in USP’s own page as of June 2023)

Certificate of analysis

No

1. Costco: Kirkland Signature Extra Strength D3 50 mcg, 600 softgels (item 393914). Maker’s page. Price ($14.99 online, with a $2.50 savings through 15 November 2026), ingredients and the USP Verified statement as seen 2026-10-23. Shown as unavailable online. Open ↗ (opens in a new tab)
2. NIH Dietary Supplement Label Database: Kirkland Signature D3 50 mcg (2000 IU), label 279473. Independent source. A federal database copy of the label (item 393914, UPC 0 96619 39391 6), entered December 2022: soybean oil, gelatin, glycerin, water, the USP Verified seal, and “Distributed by Costco Wholesale Corporation”. It shows what the label says. It is not a test. Open ↗ (opens in a new tab)
3. USP Verified brand page for Kirkland Signature (Internet Archive copy, 6 June 2023). Certifier or regulator listing. USP’s own list as archived. Lists “Vitamin D3 2000 IU Softgels” among Kirkland Signature’s USP Verified products. It does not show today’s status. Open ↗ (opens in a new tab)
4. Over-the-counter and compounded vitamin D: is potency what we expect? (JAMA Internal Medicine, 2013). Independent source. Kaiser Permanente research letter on the vitamin D content of over-the-counter bottles. The PubMed record has no abstract; the numbers are from the summary below. Open ↗ (opens in a new tab)
5. ScienceDaily: Vitamin D doses often do not match labels, study shows (2013). Independent source. Summary of the study: 55 bottles from 12 makers held 9 to 146 percent of the labeled vitamin D; the one USP-verified product was generally more accurate. Open ↗ (opens in a new tab)
6. openFDA food enforcement (recall) records for Costco. Certifier or regulator listing. Searched 2026-10-23: six food recalls (2012 to 2026), none for a dietary supplement. Open ↗ (opens in a new tab)
7. California Attorney General Prop 65 notices naming Costco Wholesale. Certifier or regulator listing. Searched 2026-10-23, 200 most recent results: foods, a leather glove and similar; none for a vitamin or supplement. Open ↗ (opens in a new tab)

• Nature Made Vitamin D3 2000 IU softgels About $11 for 90, with the USP Verified mark on its label and page. We could not find its 2,000 IU softgel in USP’s 2023 list, so it is less certain than this one.
• Momentous Vitamin D3 2000 IU About $20 for 60, with an NSF listing we opened and public lot certificates.

• Supplementation guide Article D3 vs D2, dosing recommendations, testing, and safety considerations
• The sunshine vitamin Article What vitamin D is and why deficiency is so widespread
• How to Tell if a Supplement Is Pure and Accurate Article What audits found in supplement bottles, which products are riskiest, and what third-party seals, lab certificates and FDA tools can and cannot tell you.