Klean Athlete Klean-D (5,000 IU (125 mcg), 100 Tablets) review 2027
NSF Certified for Sport — 5,000 IU (125 mcg) vitamin D3 per tablet, manufactured by Douglas Laboratories
Is the Klean Athlete Klean-D Worth It?
Best NSF Certified for Sport vitamin D3. The sport-certified counterpart to the Nature Made D3 in this ranking, at a real but higher price reflecting the stricter NSF testing standard — worth it specifically if sport certification matters to you.
Klean Athlete Klean-D Pros & Cons
- NSF Certified for Sport badge confirmed directly on the Klean Athlete brand page
- High single-tablet dose (5,000 IU) clearly disclosed
- Manufactured by Douglas Laboratories, an established supplement manufacturer
- 5,000 IU is a high dose — well above the 2,000 IU Nature Made option in this ranking, so check your total intake
- Price sourced from an authorized reseller rather than Amazon or the brand directly — confirm the live Amazon price
- Single-ingredient, so no combined multivitamin coverage
What problem does Klean Athlete Klean-D solve, and who is it for?
Klean Athlete Klean-D is a single-ingredient vitamin D3 tablet carrying the NSF Certified for Sport badge, confirmed directly on the Klean Athlete brand page. That certification is the point of the product: it is the sport-certified counterpart to the Nature Made D3 in this ranking, at a real but higher price reflecting the stricter NSF testing standard. It is worth it specifically if sport certification matters to you.
Each tablet delivers 5,000 IU (125 mcg) of vitamin D3, a high single-tablet dose that is clearly disclosed on the label. The product is manufactured by Douglas Laboratories, an established supplement manufacturer. It is intended for tested or competitive athletes wanting a certified, high-dose D3 option.
How did it score 8.8?
The score is built from four weighted criteria.
- Third-party verification: 33 out of 35. This criterion measures a USP Verified Mark, NSF Certified for Sport, or equivalent independent testing of identity, potency and purity. Klean-D holds NSF Certified for Sport, confirmed on the brand page.
- Formulation: 21 out of 25. This measures dose against the FDA Daily Value and ingredient form. Klean-D provides 5,000 IU (125 mcg) of vitamin D3 per tablet.
- Label clarity: 18 out of 20. This measures whether the supplement facts panel discloses dose, form and serving size clearly and completely. The 5,000 IU dose is clearly disclosed.
- Value: 16 out of 20. This measures price per serving against the verified dose.
What are the standout strengths?
Three strengths stand out from testing. First, the NSF Certified for Sport badge was confirmed directly on the Klean Athlete brand page, so the certification is not just a marketing claim. Second, the high single-tablet dose of 5,000 IU is clearly disclosed, which makes it straightforward to track intake. Third, the product is manufactured by Douglas Laboratories, an established supplement manufacturer.
How does NSF Certified for Sport and vitamin D3 work?
NSF Certified for Sport is an independent certification program that tests a product for identity, potency and purity, and screens for substances banned in sport. The badge means the product has been reviewed against that standard rather than only the manufacturer's own specification. Vitamin D3 is the form of vitamin D the body produces from sunlight exposure. It is a fat-soluble nutrient, and the supplement facts panel states the dose in both IU and micrograms, which is how vitamin D is labeled. This product supplies 5,000 IU (125 mcg) per tablet as a single ingredient.
How does it compare with other tested supplements?
Against Nature Made Vitamin D3 2000 IU (50 mcg), scored 8.7 at $32.49, Klean-D is ahead on score and on dose: Nature Made provides 2000 IU (50 mcg) per softgel, 250% of the FDA Daily Value, and carries the USP Verified Mark. Klean-D provides 5,000 IU (125 mcg) per tablet and carries NSF Certified for Sport.
Against Thorne Multi-Vitamin Elite (A.M./P.M.), scored 8.3 at $82.00 (thorne.com; Amazon price may differ), Klean-D is ahead on score and lower on price. Thorne is a two-formula A.M./P.M. multivitamin system with NSF Certified for Sport, while Klean-D is a single-ingredient vitamin D3 tablet.
Against Garden of Life SPORT Certified Grass Fed Whey Protein, scored 8.2 at $41.99, Klean-D is ahead on score and lower on price. Garden of Life is a protein powder listed as NSF Certified for Sport on NSF's own official certified-products directory, with 24g grass-fed whey isolate, 6g BCAAs and 4g glutamine/glutamic acid per serving.
| Klean Athlete Klean-D | Nature Made Vitamin D3 2000 IU (50 mcg) | Thorne Multi-Vitamin Elite (A.M./P.M.) | Garden of Life SPORT Certified Grass Fed Whey Protein | |
|---|---|---|---|---|
| Our score | 8.8 | 8.7 | 8.3 | 8.2 |
| Type | Vitamin D3 | Vitamin D3 | Multivitamin | Protein powder |
| Dose per serving | 5,000 IU (125 mcg) per tablet | 2000 IU (50 mcg) per softgel, 250% DV | – | 24g whey protein isolate, 6g BCAAs, 4g glutamine/glutamic acid per serving |
| Third-party certification | NSF Certified for Sport | USP Verified Mark | NSF Certified for Sport | NSF Certified for Sport |
Where does it fall short?
The 5,000 IU dose is high — well above the 2,000 IU Nature Made option in this ranking, so check your total intake. The price was sourced from an authorized reseller rather than Amazon or the brand directly, so confirm the live Amazon price. It is also single-ingredient, so it provides no combined multivitamin coverage.
Is the price worth it?
The price summary is $17.50 from an authorized reseller, with the caveat to check the live Amazon price. That figure reflects the stricter NSF testing standard compared with the USP Verified Nature Made option, and the value criterion scored 16 out of 20.
Who should buy Klean Athlete Klean-D?
It is right for tested or competitive athletes wanting a certified, high-dose D3 option. If you need NSF Certified for Sport in a single-ingredient vitamin D3 tablet and want the 5,000 IU dose clearly disclosed, this is the fit. If you want a lower dose or combined multivitamin coverage, the alternatives above are the better match.
Klean Athlete Klean-D at a Glance
Rubric v1: Third-party verification 35 · Formulation 25 · Label clarity 20 · Value 20. Score = Σ ÷ 10, locked Sep 21, 2026. How we rank.
Where to buy — prices checked Sep 22, 2026
Klean Athlete Klean-D specifications
Where it loses
Price sourced from a reseller, not confirmed on Amazon directly.
Still the right pick for
Tested or competitive athletes wanting a certified, high-dose D3 option.
What owners say
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