RetzlerRx® Vitamin D3 Plus K2 combines high-potency vitamin D3 with two forms of vitamin K in a convenient once-daily softgel. Each serving provides 5,000 IU of vitamin D3 as cholecalciferol, 20 mcg of vitamin K1 as phytonadione USP, and 90 mcg of vitamin K2 as menaquinone-7 (MK-7).
Vitamin D3 helps the body absorb calcium and supports bone strength, normal muscle function, and immune function.* Vitamin K works through a different pathway, activating proteins involved in normal blood clotting, bone mineralization, and calcium regulation.* Combining them provides a practical option for adults whose vitamin D and vitamin K needs are appropriately matched to this formulation.
- Vitamin D3: 5,000 IU as cholecalciferol
- Vitamin K1: 20 mcg as phytonadione USP
- Vitamin K2: 90 mcg as menaquinone-7 (MK-7)
- Serving size: 1 softgel
- Servings per bottle: 60
- Typical bottle duration: Approximately 60 days
Why Combine Vitamin D3 and Vitamin K?
Vitamin D and vitamin K are often grouped together because both participate in calcium physiology, but they do different jobs.
Vitamin D3 increases intestinal calcium absorption. That is one reason adequate vitamin D status is important for normal bone mineralization and skeletal health.* Vitamin D also contributes to normal muscle and immune function.*
Vitamin K participates in what happens after calcium is available. Vitamin K-dependent proteins include osteocalcin, which is involved in bone mineralization, and matrix Gla protein, which participates in normal calcium regulation within vascular tissues.*
The relationship is complementary rather than magical. Taking vitamin K2 does not make every dose of vitamin D appropriate, and vitamin K2 should not be described as removing existing calcium from arteries. The useful question is whether the amount and form of each nutrient fit the individual taking them.
For a deeper look at the evidence, see Vitamin D3 and K2: Do You Really Need Them Together?
Why This Formula Includes Both K1 and K2
Vitamin K is a family of related compounds rather than a single nutrient.
Vitamin K1, or phylloquinone/phytonadione, is the form most closely associated with normal blood-clotting physiology.* This formula supplies 20 mcg of vitamin K1 as phytonadione USP.
Vitamin K2 refers to a group of menaquinones. RetzlerRx® Vitamin D3 Plus K2 uses menaquinone-7, or MK-7, at 90 mcg per softgel. MK-7 remains in circulation longer than some other forms of vitamin K and is commonly used in once-daily formulas designed around bone and calcium metabolism.*
You can read more about this pathway in our clinical education article, Vitamin K2 and Longevity: Calcium Direction, Bone Health, and Cardiovascular Support.
What Does 5,000 IU of Vitamin D3 Mean?
This is a high-potency vitamin D formula. It is not intended to suggest that every adult should routinely take 5,000 IU per day.
Vitamin D requirements vary with baseline vitamin D status, sunlight exposure, diet, age, body composition, absorption, medications, kidney function, medical history, and other supplements being used.
The adult tolerable upper intake level established for routine unsupervised intake is 4,000 IU per day. Higher amounts may be used under clinical supervision when appropriate. Because this product supplies 5,000 IU per softgel, long-term use should be individualized rather than automatically added to every supplement routine.
The manufacturer specifically advises laboratory monitoring during regular use of this high-potency formula. At HormoneSynergy®, we prefer the same measurement-driven approach: test when appropriate, supplement for a reason, and adjust according to the person rather than simply assuming that more vitamin D is better.
Bone Health Requires More Than Vitamin D
Vitamin D is important for skeletal health, but bone density is influenced by far more than a single nutrient. Hormone status, resistance exercise, protein intake, calcium and magnesium intake, muscle mass, medications, age, menopause, testosterone status, and metabolic health all influence the skeleton over time.
This is especially important for people with osteopenia or osteoporosis. A supplement should not substitute for actually measuring bone density or identifying why bone is being lost.
Our broader approach is discussed in Bone Density and Osteoporosis Prevention in Longevity Medicine.
Who May Consider RetzlerRx® Vitamin D3 Plus K2?
This formulation may be considered by adults seeking nutritional support for:
- Bone strength and normal bone mineralization*
- Healthy calcium absorption and utilization*
- Normal muscle function*
- Normal immune function*
- Vitamin K-dependent calcium regulation*
- Cardiovascular wellness as part of a broader prevention strategy*
- A convenient combined vitamin D3, K1, and K2 formula*
Whether 5,000 IU of vitamin D3 is appropriate should be based on the individual rather than the product category alone.
RetzlerRx® Vitamin D3 Plus K2 vs. Synergy D3K2 PRO
We carry more than one vitamin D3 and K2 formulation because people do not always need the same amount of vitamin K.
| Formula | Vitamin D3 | Vitamin K1 | Vitamin K2 MK-7 |
|---|---|---|---|
| Vitamin D3 Plus K2 | 5,000 IU | 20 mcg | 90 mcg |
| Synergy D3K2 PRO | 5,000 IU | — | 180 mcg |
Neither formula is automatically “better.” Vitamin D status, dietary vitamin K, medications, anticoagulant use, other supplements, bone-health goals, and the broader clinical picture should determine which combination makes sense.
Supplement Facts
| Serving Size | 1 Softgel |
| Servings Per Container | 60 |
| Vitamin D | 5,000 IU as cholecalciferol |
| Vitamin K1 | 20 mcg as phytonadione USP |
| Vitamin K2 | 90 mcg as menaquinone-7 (MK-7) |
Other Ingredients: Olive oil, gelatin, glycerin, beeswax, water, annatto extract (color), medium-chain triglyceride oil, and d-alpha tocopherol (antioxidant).
Quality and Dietary Information
- Non-GMO Project Verified
- Certified gluten-free
- Dairy-free
- No artificial colors
- Free from artificial preservatives
- Professional supplement manufacturing and quality-control standards
- Ingredient and finished-formula testing for identity, purity, strength, and stability
Suggested Use
Take 1 softgel daily or as directed by your healthcare practitioner.
Because vitamins D and K are fat-soluble, the softgel may be taken with a meal containing dietary fat. Do not exceed the recommended dosage unless directed by a qualified healthcare professional.
At one softgel per day, a 60-softgel bottle provides approximately a 60-day supply.
Important Cautions
Vitamin K and anticoagulants: Do not begin, stop, or substantially change vitamin K supplementation without medical guidance if you use warfarin or another vitamin K-antagonist anticoagulant. Changes in vitamin K intake can affect anticoagulation control.
High-potency vitamin D: This product provides 5,000 IU of vitamin D3 per serving. Review other vitamin D-containing supplements before use to avoid unintended duplication. Periodic laboratory monitoring may be appropriate during regular high-dose supplementation.
Consult your healthcare professional before use if you are pregnant or breastfeeding, have kidney disease, elevated blood calcium, a history of kidney stones, or take prescription medications. Keep out of reach of children.
Why RetzlerRx®?
RetzlerRx® supplements are selected and developed within a physician-led longevity medicine practice. Our goal is not to build the largest supplement stack possible. It is to use appropriate nutrients, meaningful doses, quality ingredients, and clinical judgment when supplementation has a legitimate role.
Dr. Kathryn Retzler may use vitamin D and vitamin K as part of a broader plan involving laboratory assessment, bone density, hormone status, nutrition, resistance exercise, muscle preservation, and cardiovascular risk. The supplement is one piece of that picture.
For more perspective on how we approach supplementation, read The Practical Longevity Supplement Stack: What We Use and Why.
Frequently Asked Questions
How much vitamin D3 is in each softgel?
Each softgel provides 5,000 IU of vitamin D3 as cholecalciferol.
How much vitamin K2 is in RetzlerRx® Vitamin D3 Plus K2?
Each softgel contains 90 mcg of vitamin K2 as menaquinone-7 (MK-7). It also contains 20 mcg of vitamin K1 as phytonadione USP, for 110 mcg of total vitamin K.
Is the product 110 mcg of K2?
No. The formula contains 110 mcg of total vitamin K, consisting of 20 mcg of vitamin K1 plus 90 mcg of vitamin K2 as MK-7. The K2 portion itself is 90 mcg.
Why are vitamin D3 and vitamin K2 combined?
Vitamin D3 supports calcium absorption, while vitamin K2 supports vitamin K-dependent proteins involved in bone mineralization and normal calcium regulation.* The nutrients have complementary roles, although that does not mean everyone taking vitamin D requires the same amount of K2.
Does vitamin K2 remove calcium from the arteries?
No. Vitamin K2 participates in the activation of proteins involved in normal vascular calcium regulation, but it should not be described as removing established arterial calcium or treating coronary artery disease.
Is 5,000 IU of vitamin D3 considered a high dose?
Yes. Five thousand IU is a high-potency daily amount and is above the adult tolerable upper intake level established for routine unsupervised intake. It may be appropriate in selected individuals under clinical guidance, particularly when vitamin D status is being monitored.
Can I take this with another vitamin D supplement?
Possibly, but first calculate the total amount of vitamin D from all supplements. This formula already supplies 5,000 IU per softgel, so adding additional vitamin D can produce unnecessarily high intake.
Can I take RetzlerRx® Vitamin D3 Plus K2 with warfarin?
Do not begin or substantially change vitamin K supplementation without guidance from the clinician managing your anticoagulation. Both vitamin K1 and vitamin K2 can interfere with vitamin K-antagonist medications such as warfarin.
Should I take it with food?
Vitamin D3 and vitamin K are fat-soluble nutrients. This softgel may be taken with a meal containing dietary fat unless your healthcare practitioner directs otherwise.
How long does one bottle last?
Each bottle contains 60 softgels. At the suggested use of one softgel daily, one bottle lasts approximately 60 days.
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.
The information provided is for educational purposes and is not a substitute for individualized medical advice. Dietary supplements should be selected in the context of medical history, medications, laboratory findings, diet and other supplements being used.