Summary
What should I look for when buying a vitamin D3 + K2 supplement?
Compare the amount of vitamin D3 and K2 per daily serving, the forms used, ingredient sources, dietary suitability, quality assurance, safety warnings and cost per day. Vitamin D contributes to normal calcium absorption and bone maintenance, while vitamin K contributes to normal blood clotting and bone maintenance. A higher dose is not necessarily better for everyone. [1, 2]
What is the difference between vitamin D3 + K2 1000iu and 2000iu?
The main difference is the amount of vitamin D3. A 1000iu capsule supplies 25µg of vitamin D3, while a 2000iu capsule supplies 50µg. Both Nature's Best formulas supply 90µg of vitamin K2 per capsule. The appropriate option depends on your existing intake, circumstances and professional advice, rather than strength alone. [1, 4, 5]
Does vitamin D3 need to be taken with vitamin K2?
No. Vitamin D3 does not universally need to be taken with vitamin K2. They perform different functions in the body, and research has investigated whether combining them can improve bone outcomes. A meta-analysis of eight randomised controlled trials involving 971 participants reported improvements in some bone mineral density measures, but the evidence does not establish that every person benefits from taking both vitamins together. [2, 6]
Is vitamin D3 + K2 safe to take every day?
Daily use can be appropriate when the product, dose and individual's circumstances are suitable, and the label's directions are followed. Excessive vitamin D intake can cause undesirable increases in blood calcium. Vitamin K supplements can also interact with warfarin and similar anticoagulants. Check your total vitamin D intake and seek professional advice if you take medication, have a relevant medical condition, or are pregnant or breastfeeding. [1, 2, 7]
What to compare before buying vitamin D3 + K2
Vitamin D and vitamin K have different but complementary roles in the body. Vitamin D contributes to normal calcium absorption and the maintenance of normal bones, while vitamin K contributes to normal blood clotting and the maintenance of normal bones. [1, 2]
However, a supplement containing both vitamins is not automatically more effective for every person than taking vitamin D alone. When comparing products, focus on the labelled nutrient amounts, the formulation, suitability for your diet, safety information and cost per daily serving.
1. Dose: Compare the amount of each vitamin per serving
The first thing to check is how much vitamin D3 and vitamin K2 you receive in the recommended daily serving. A higher dose is not automatically a better choice; the appropriate amount depends on your circumstances, existing intake and any advice from a healthcare professional. [1, 3]
In the UK, adults are advised to consider taking 10µg (400iu) of vitamin D daily during autumn and winter. People with limited sunlight exposure or darker skin may need supplementation throughout the year. [3]
Nature's Best offers two D3 + K2 formulations with different vitamin D strengths. [4, 5]
| Comparison | D3 1000iu + K2 90µg | D3 2000iu + K2 90µg |
|---|---|---|
| Vitamin D3 per capsule | 25µg (1000iu) | 50µg (2000iu) |
| Vitamin K2 per capsule | 90µg | 90µg |
| Labelled adult use | 1–2 capsules daily with a meal | R1 capsule daily with a meal |
| Key distinction | Lower vitamin D strength | Higher vitamin D strength |
| Product page | View 1000iu formula | View 2000iu formula |
Always check the current label for serving instructions and formulation details.
What to look for: Compare the amount per capsule and the total amount in your daily serving, rather than relying on terms such as “high strength” or “maximum strength”.
For context, the adult tolerable upper intake level according to the NHS is 100µg (4000iu) of vitamin D daily from all sources. This is a safety ceiling, not a recommended target, and individual circumstances may require professional healthcare advice. [1]
2. Vitamin D3 and K2 forms: Check the label and ingredient source
The names and forms of the vitamins matter because they tell you what the supplement contains and help you compare like with like.
- Vitamin D3 (cholecalciferol): Vitamin D helps the body absorb calcium and supports normal bones and muscle function. Vitamin D3 is also produced in human skin in response to suitable UVB exposure. [1]
- Vitamin K2 (menaquinone): Vitamin K is involved in the activation of proteins associated with blood clotting and bone metabolism. K2 is a family of compounds, including MK-4 and MK-7, rather than a single ingredient. [2]
- MK-7: This is one of the best-studied forms of vitamin K2. Its properties differ from those of MK-4, but differences in absorption or persistence do not by themselves establish superior outcomes for every consumer. [2, 6]
Nature's Best identifies the D3 in both of its combination products as cholecalciferol and the K2 as menaquinone-7 (MK-7), sourced from chickpeas. The formulas also contain sunflower seed oil to optimise the absorption of these fat soluble nutrients. [4, 5]
What to look for: Choose a product that names both vitamin forms and clearly identifies ingredient sources where these are established. If the source matters to you, look beyond the front-of-pack claims and check the complete ingredient list.
3. Dietary suitability: Check whether the complete formula fits your diet
A supplement's vitamin source is only one part of its dietary suitability. Capsule shells, carriers and other ingredients can affect whether a product is suitable for vegetarians, vegans or people avoiding particular ingredients.
Nature's Best lists both D3 + K2 combination products as suitable for vegetarians but not suitable for vegans. Its product information also states that they are not suitable during pregnancy or breastfeeding. [4, 5]
Before purchasing, check:
- Vegetarian or vegan requirements: Confirm the manufacturer's stated suitability for the complete formula rather than assuming that a plant-derived K2 makes the whole product vegan.
- Allergens and sensitivities: Review the full ingredients and allergen declarations on the current packaging.
- Capsule ingredients: Check the capsule shell, carriers, oils, colourings and gelling agents if these matter to your dietary requirements.
- Pregnancy and breastfeeding: Follow the product-specific warnings and seek professional advice about an appropriate supplement.
What to look for: Clear, specific dietary suitability information that reflects the entire product, not just its headline ingredients.
4. Quality assurance: Look beyond marketing claims
Quality assurance helps customers assess whether a supplement is made to consistent standards and is clearly labelled. A professional-looking label or a claim such as “premium quality” is not, by itself, proof of product quality.
When comparing vitamin D3 + K2 supplements, look for:
- Manufacturing standards: Check whether the manufacturer specifies where the product is made and which quality-management or manufacturing standards apply.
- Ingredient transparency: Confirm that the label names the vitamin forms, quantities per serving and other ingredients.
- Batch traceability: Look for batch identification, a best-before date and clear manufacturer details.
- Clear instructions: A reputable product should state the recommended daily dose, relevant warnings and storage requirements. [7]
Nature's Best states that its D3 + K2 products are manufactured in the UK under Good Manufacturing Practice (GMP) standards. This is a manufacturer statement; customers seeking additional assurance can ask what testing and batch-specific documentation are available. [4, 5]
What to look for: Specific, verifiable quality information rather than relying on broad claims about purity, absorption or superiority.
5. Safety: Check interactions, existing intake and personal circumstances
Even commonly used vitamins can cause problems if taken in excessive amounts or alongside certain medicines. Before choosing a D3 + K2 supplement, consider your total nutrient intake and whether you need professional advice. [1, 2, 7]
Vitamin D safety
The UK adult upper intake level is 100µg (4000iu) daily from all sources, unless a healthcare professional has recommended a different regimen for a specific medical reason. [1]
Check whether you already take vitamin D in a multivitamin, standalone supplement or another product. Avoid unintentionally combining several high-dose products.
Vitamin K and anticoagulants
Vitamin K can interact with warfarin and similar vitamin K antagonist anticoagulants. Changes in vitamin K intake can affect how these medicines work. Anyone taking these medicines should seek advice from their healthcare provider before using a vitamin K supplement. [2]
When to seek advice
Speak to a healthcare professional before starting a supplement if you:
- Take regular prescription medicines.
- Have a medical condition that may affect vitamin D or calcium regulation.
- Are pregnant or breastfeeding.
- Have been diagnosed with vitamin D deficiency and need a treatment dose.
- Are unsure whether the supplement duplicates nutrients in other products. [1, 7]
Nature's Best specifically advises against taking its D3 + K2 products with anticoagulants except on a doctor's advice, and states that these products are not suitable during pregnancy or breastfeeding. Check the current product label before use. [4, 5]
What to look for: Prominent warnings, an appropriate dose and clear guidance for people taking medication. Do not treat a higher dose as a substitute for individual medical advice.
6. Use: Choose a supplement that fits your routine
The best supplement choice is one you can use correctly and consistently, provided it is appropriate for your needs.
Nature's Best recommends taking its D3 + K2 capsules with a meal. The 1000iu product label specifies one to two capsules daily, while the 2000iu product specifies one capsule daily, with two capsules recommended only for short-term use. Always follow the current label and do not exceed its recommended intake. [4, 5]
Vitamin D and vitamin K are fat-soluble vitamins. Taking them with a meal is a practical way to incorporate supplementation into a regular routine; the product formulation and your overall dietary intake also matter. [1, 2, 4, 5]
Before choosing, consider:
- Daily convenience: Will you remember to take the supplement with a meal?
- Capsule format: Is the size and format comfortable for you?
- Serving size: Does the recommended daily amount match your needs without unnecessary extra capsules?
- Storage: Can you follow the label's storage instructions and keep the product out of reach of children? [7]
What to look for: Clear daily instructions, a manageable serving size and a routine that is easy to maintain.
7. What level should you choose? - Vitamin D3 + K2: 1000iu vs. 2000iu Comparison
| Feature / Metric | Vitamin D3 (1000iu) + K2 90µg | Vitamin D3 (2000iu) + K2 90µg |
|---|---|---|
| Primary Intent | Maintaining stable baseline levels for adults who already have adequate vitamin D blood status. | Actively raising insufficient levels or providing a stronger daily dose. |
| Sun Exposure Link | Ideal for the spring and summer months when natural synthesis from sunlight is higher. | Ideal for the late autumn and winter months when sun exposure is minimal or non-existent. |
| Dietary Context | Best if you already eat a diet rich in fortified foods, eggs, fatty fish, and dairy. | Necessary if your diet lacks vitamin D and you rely entirely on supplements for your daily intake. |
| Body Weight & Absorption | Suitable for individuals with a standard body mass index (BMI) who absorb nutrients easily. | Often preferred for older adults or individuals with a higher BMI, as body fat can sequester vitamin D. |
| Stacking Safety | Highly flexible if you want to combine it with a separate multivitamin without over-supplementing. | Best used as a standalone target supplement to avoid accidentally hitting the upper daily limit (4000iu). |
8. Value: Compare cost per daily serving, not just the pack price
The cheapest bottle is not necessarily the best-value option. Pack size, daily serving, nutrient strength and the suitability of the dose all affect the overall value.
Use this calculation to compare products fairly:
"Cost per day" = "Pack price" / "Number of daily servings"
For example, a bottle containing 60 capsules provides 60 days of use at one capsule per day, but only 30 days at two capsules per day.
When comparing Nature's Best products with alternatives, consider:
- Cost per day: Calculate the price based on the recommended daily serving.
- Cost per month: Multiply the daily cost by 30 for a simple monthly comparison.
- Nutrient amounts: Compare vitamin D3 and K2 separately, not just total capsule strength.
- Ingredient transparency: Consider whether the forms and sources are clearly identified.
- Dietary suitability: Avoid paying for a product that does not meet your dietary requirements.
- Quality information: Assess whether manufacturing and testing information is available.
Nature's Best lists its combination formulas and standalone K2 supplement in its vitamin K collection. Compare the current prices, pack sizes and recommended serving instructions on the individual product pages, as offers and prices may change. [4, 5, 8]
What to look for: A product that meets your requirements at a reasonable cost per appropriate daily serving, rather than one selected solely for the highest strength or lowest headline price.
Need expert advice? Contact our Nutrition Advice team if you have any questions about Nature’s Best Vitamins D3 & K2 and for further help choosing from the range.
References
1. NHS (2020). Vitamin D - vitamins and minerals. [online] NHS. Available at: https://www.nhs.uk/conditions/vitamins-and-minerals/vitamin-d/
2. National Institutes of Health, Office of Dietary Supplements. Vitamin K: Fact Sheet for Health Professionals. Information on vitamin K forms, physiological functions, bone research and anticoagulant interactions. https://ods.od.nih.gov/factsheets/VitaminK-HealthProfessional/
3. UK Government, Office for Health Improvement and Disparities. Vitamin D deficiency: migrant health guide. UK public health guidance on recommended vitamin D supplementation and groups at increased risk of deficiency. https://www.gov.uk/guidance/vitamin-d-deficiency-migrant-health-guide
4. Nature's Best. Vitamin D3 1000 IU and K2 90 µg. Manufacturer's product specifications, ingredients, dietary suitability, directions and warnings. https://www.naturesbest.co.uk/products/vitamins-d3-1000iu-and-k2-90g-high-strength-formula
5. Nature's Best. Vitamin D3 2000 IU & K2 90 µg Maximum Strength Formula. Manufacturer's product specifications, ingredients, dietary suitability, directions and warnings. https://www.naturesbest.co.uk/products/vitamin-d3-2000iu-k2-90g-maximum-strength-formula
6. Huang ZB, et al. (2020). The combination effect of vitamin K and vitamin D on human bone quality: a meta-analysis of randomized controlled trials. Eight randomised controlled trials involving 971 participants. Journal of Orthopaedic Surgery and Research. https://pubmed.ncbi.nlm.nih.gov/32219282/
7. UK Government, Department of Health and Social Care. Food supplements guidance for consumers. Guidance on responsible supplement use, label instructions, high-dose products, medicine interactions and purchasing from reputable suppliers. https://www.gov.uk/government/publications/food-supplements-guidance-for-consumers
8. Nature's Best. Vitamin K Supplements for Bone & Heart Health. Collection page listing the brand's vitamin K and D3 + K2 products. https://www.naturesbest.co.uk/collections/vitamin-k