Bio-Avail D3/K2
A Highly Absorbable Blend of Vitamins D3 and K2
Bio-Avail D3/K2
A Highly Absorbable Blend of Vitamins D3 and K2
Restore optimal D3 and K2 levels with this clean, easy-to-absorb, liquid formula.
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Supercharge your immune, metabolic, cardiovascular, and bone health
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Flexible dosing: 1,000 IU of D3 and 120 mcg of K2 per one-drop serving
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Only 3 ingredients: MCT oil, D3, and K2. No artificial fillers or junk!
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High-potency formula (600 servings per bottle!) saves you money and time.
Overcome Vitamin D Inadequacy (>90% of Americans)
Support immune function, heart and metabolic health, mood, cognitive function, strong bones
Protect Your Bones and Heart
Experience the synergistic benefits of D3 and K2 for cardiovascular and bone health.
Fine-Tune Your Daily Dose
With 1,000 IU of D3 and 120 mcg of K2 per drop, our flexible liquid formula makes it easy to get exactly the amount you need.
Affordable and Efficient D3/K2 Benefits
Our high-potency formula provides a clean source of D3/K2 at less than 6 cents per serving.
Powerful Nutrients & Vitamins
Vitamin D3
1,000 IU of vitamin D3 in a highly absorbable, liquid form. Avoid seasonal fluctuations of vitamin D levels and optimize your intake no matter where you live or what time of year it is.
Vitamin K2
120 mcg of vitamin K2 in MK-4 form. Get the full benefits of vitamin K2 by taking one of the most effective forms.
MCT Oil
MCT oil is a perfect carrier for D3 and K2 because it is rapidly absorbed and is a great energy source. It has a clean, neutral taste with no sweeteners, artificial flavors, binders, or fillers.
Signs You Need Bio-Avail D3/K2
Frequent colds & flu
Low mood
Weak bones
Metabolic difficulties
Brain fog, poor memory
Cardiovascular risk
What You'll Feel Using Bio-Avail D3/K2
90-Day Money Back Guarantee
We're confident you'll love our products, but if you're not completely satisfied, we offer a 90-Day, 100% money-back guarantee on all purchases. Simply contact us for a full refund, no questions asked. Buy with confidence knowing you're covered by our guarantee.
The Adapt Naturals Standard
In our increasingly toxic world, the last thing you want to worry about is a lot of artificial junk in your supplements. Adapt Naturals supplements are made with the cleanest possible ingredients, without gluten or GMOs. Our products are manufactured in a U.S. facility that meets the NSF’s rigorous GMP regulatory standards.
Third-Party Lab-Tested with Transparent Results
We conduct third-party testing on all our products to verify their purity, potency, and safety. Most importantly, we transparently share these results with our customers by posting Certificates of Analysis (COAs) and test results directly on our website. We want you to have full confidence that you’re getting exactly what you think you are with each purchase.
See Test Results
Meet Chris Kresser, your
Trusted Health & Wellness Guide
Founder & Functional Medicine Clinician
- Globally renowned expert with over 15 years of experience
- Dedicated to helping people improve their health by addressing modern challenges and nutrient gaps
Author & Educator
- Treated thousands of patients
- Trained more than 2,000 healthcare professionals
- Gained valuable insights into functional medicine and nutrition
Unlock Your Optimal Health
Upgrade Your Wellness with Bio-Avail D3/K2—Lifelong Health, Simplified
Get Healthier & Happier - Try Now
Your Questions Answered
i ordered extra so I do NOT run out again. I can tell the difference in 3D/K2 product. I bought another kind when adapt ran out. I did not feel great. 3D/K2 has helped me conquer SAD. I feel great!!! Helps so much when feeling low energy. Usually Jan and Feb are my worst months. Not this year!!! Keeping stocked up!!
Hey Marianne,
This is amazing—we're so thrilled Bio-Avail D3/K2 has helped you conquer SAD and feel great during your typically worst months! The fact that you ordered extra so you don't run out and noticed the difference when you tried another brand really shows how powerful the right form and quality makes. Chris pairs vitamin D3 with K2 for optimal absorption and proper calcium metabolism. We're so happy you're feeling energized and not low anymore!
I love Bio-Avail D3/K2 for its natural ingredients, purity, and sustainability focus–key priorities for me. The D3 and K2 combo offers health benefits I value. It’s exciting to find a supplement that matches my values so well. I’d recommend it to anyone who cares about clean, eco-friendly options.
Hi Samantha! Thank you for sharing this thoughtful review! Bio-Avail D3/K2 was designed with these exact values in mind—pure, potent, and sustainably sourced. This combination of D3 and K2 supports bone health, immune function, and cardiovascular resilience, making it a smart, eco-friendly addition to any wellness routine. We’re so glad it’s a perfect match for you!
This is our first time using these supplements and I'm so glad we got them! They are third party tested, so they actually say what they are and are CLEAN! The omegas are easy to swallow and don't have any fishy after taste. The vitamin d/k is really great to just put in your morning lemon water with breakfast and so easy to drop in! We will definitely be adding these supplements to our lifestyle in the long run!
Hi Julie,
Thanks for this great review! Love hearing that the D3/K2 drops work so well in your morning lemon water. And you're absolutely right about the testing - we're serious about keeping each product clean and pure. So glad you've found supplements that fit easily into your routine!
Great line of supplements that takes the guess work out of what to purchase in regard to, quality, absorption, quantity, benefits etc. Tons of free information and advice that comes along with ordering the adapt products and a real sense of overall well being in taking them. I was a bit hung up on the cost initially but it’s better to start investing towards my health than to be dealing with medical &
pharmaceutical routes if I don’t. I trust I’ve made the right choice. Thanks for giving that peace of mind!!
Hi Shannon, Thank you for trusting our brand. Chris has done a lot of work and research to ensure he is providing customers with high quality products that is beneficial to their health. We are happy you found our supplements along with the information to be beneficial. We hope you experience great benefits from these supplements. We appreciate your review!
I had been using a name brand vitamin D/K2 product for years and recently switched to Adapt Natural’s. I appreciate the ease of using the dropper to dispense the liquid and know it is a high quality product.
Hey Victoria,
Switching from a name brand after years and appreciating both the ease of the dropper and the confidence in the quality is such a meaningful vote of trust and we are grateful for it! The liquid form delivering D3 from sheep lanolin and MK-4 K2 made from geraniol in a clean MCT oil base is exactly the kind of simple and pure formula Chris designed it to be. Thank you so much for sharing!
My home state of wa does not have enough sun. Regular vitamin D supplements were not moving the needle, but these do
Hey Cyndy,
Living in Washington where the sun just does not cooperate and finally finding a D3 that actually moves the needle is such a practical win! The liquid form delivers 1000 IU of D3 alongside 120 mcg of MK-4 K2 in a single drop and the bioavailability of the liquid form really does make a meaningful difference compared to many standard capsule supplements. We are so glad it is working for you and thank you for sharing!
One tiny drop for a full dose of vitamin D3/K2! The hard part is avoiding an accidental double dose.
I love the ingredient list, but I am unfortunately allergic to coconut, so it's not for me. I bought this for family members and I started taking it this week following labs showing my vitamin D is low, thinking "one drop of highly refined coconut oil is fine". By midmorning day 4 I was itching internally and externally and feeling slightly dizzy / foggy. I'm better after a dose of charcoal and plenty of water, but apparently my coconut allergy is real. So, I just need the exact same thing with olive oil and I'll be good to go!
For all you normal people, this is the best.
Hi Melissa,
So sorry to hear about your allergic reaction! We're happy to hear your family members are able to enjoy the benefits of our D3/K2 as an alternative. We will keep an olive oil version in mind! Thanks for sharing your experience and we wish you the best of luck on your health journey!
I know and believe in the healthy value of D3/K2. And I am appreciative.
Hey there,
Believing in the value of D3 and K2 working together and appreciating a formula that delivers both in their most bioavailable forms is something we are so grateful to hear. That trust means everything to us and we are so glad it is part of your routine. Thank you so much for sharing!
Using the drops is a nice way to avoid having to take yet another pill.
Hey Patricia,
Avoiding yet another pill with the liquid drops is such a practical win and one drop delivering 1000 IU of D3 and 120 mcg of MK-4 K2 together makes it one of the most efficient additions to any stack. We are so glad it is working seamlessly for you and thank you for sharing!
I love the liquid form of this supplement, which avoids any unnecessary fillers! However, after reading Kate Rhéaume-Bleue's "Vitamin K2 and the Calcium Paradox", I can't help but wonder if the formulation is inadequate in terms of Vitamin K2. According to the book, MK-4 is synthetic and its recommended daily dose is 45 mg (i.e., 45,000 mcg), ideally split into 3 servings throughout the day due to its low half-life. To meet that recommended dose, one would have to drink more than a half of the bottle in a day, which would, of course, mean an overdose of vitamin D3. In contrast, the recommended dose of MK-7, extracted from natto, is 120 mcg, and once per day thanks to its much longer half-life.
Now, the book is 14 years old, so I wonder if there is some more recent research on MK-4 dosage that justifies the tiny amount of MK-4 in this supplement. That being said, I checked MK-4 supplements on Amazon, and most of them are in the 15-45 mg (i.e., 15,000-45,000 mcg) range per softgel.
So, that makes me wonder if I have been taking a meaningless dose of K2 ever since I switched from my MK-7 supplement to this supplement a couple of years ago. Please correct me if I'm wrong, but the formulation either needs to change to MK-7 or the MK-4 concentration needs to increase at least 100-fold in order for it to have therapeutic effect.
Hi Jurik!
Thanks so much for such a thoughtful, well-researched review. We really appreciate customers who dig into the science behind their supplements the way you have.
We always suggest talking with your healthcare provider about dosing questions specific to your own health goals, since the right amount can vary quite a bit from person to person. That said, we’re glad to share some general context here.
The 45 mg (45,000 mcg) daily MK-4 amount referenced in Kate Rhéaume-Bleue’s book reflects a specific line of clinical research—largely out of Japan—studying high-dose MK-4 (menatetrenone) as a pharmaceutical-level protocol, split into multiple daily doses because of its short half-life at that amount. That’s a different context than the amount included in a typical daily D3/K2 supplement, which is formulated in the mcg range as part of general nutritional support alongside D3, rather than to replicate a high-dose clinical protocol.
We appreciate you taking the time to share this with us!
I love how this vitamin D3 is also paired with K2. It is great!
Hey Alyssa,
D3 paired with K2 is such a smart combination and we are so glad you love it! Chris included K2 specifically because it works synergistically with D3 to direct calcium to the bones and teeth where it belongs rather than allowing it to accumulate in soft tissues. They really are better together and we are glad that is landing for you. Thank you for sharing!
I just started taking this so I can't arrest to it making any difference yet. Just wanted to make a suggestion to put the actual measurement on the dropper, i.e., 0.5 ml, etc.
Hey there,
That is such a helpful and practical suggestion and we really appreciate you taking the time to share it! Putting clear measurement markings on the dropper is a really sensible idea especially for a liquid formula where precision matters. We are passing this feedback along to our team. Thank you and we hope you start noticing the benefits soon!
Waiting to see results
Hey Breanna,
Thanks for giving Bio-Avail D3/K2 a try! Vitamin D benefits often build gradually over time as your levels optimize. Many people notice improvements in energy, mood, and immune resilience over several weeks to months of consistent use. Chris pairs D3 with K2 for optimal absorption and proper calcium metabolism. Keep going! We're hopeful you'll start noticing positive changes!
Good Vit D but could be a bigger bottle
Hey James,
Thank you for the feedback! We're glad the Vit D3/K2 is working well for you. We appreciate the suggestion about a bigger bottle—we'll definitely pass that along to our team as we continue improving our products!
Simple way to take vitemin D3 and K2
Hey Tammy!
Thanks so much for sharing your feedback on Bio-Avail D3/K2! We're thrilled to hear you're enjoying it!
You're absolutely right - we designed this product to make it simple and convenient to get both vitamin D3 and K2 together. These two nutrients work synergistically, with K2 helping to direct calcium to your bones where it belongs (rather than soft tissues), while D3 supports calcium absorption and immune function. Having them combined in one easy-to-take supplement makes it effortless to support your bone health, cardiovascular health, and overall wellness.
Thanks again for taking the time to leave a review. We really appreciate your support!
Love the combination of D3/K2. So easy to take in liquid drop form.
Hi there,
Thank you so much for taking the time to leave us a 5-star review! We're thrilled to hear that you're loving the Bio-Avail D3/K2 combination. The liquid drop form really does make it convenient and easy to incorporate into your daily routine, and we're so glad that's working well for you.
The synergistic pairing of vitamin D3 and K2 is designed to work together to support optimal calcium absorption and bone health, so you're giving your body exactly what it needs in the most bioavailable form. We appreciate your support and hope Bio-Avail D3/K2 continues to be a valuable part of your wellness routine!
I just started using it, and like it
Hi Eva,
Thank you so much for sharing your feedback! We're thrilled to hear you're enjoying the Bio-Avail D3/K2. Welcome to the Adapt Naturals family! Take good care!
in 3 month my Vitamin d level of 23 improved to 58 !
Hi Gabriella,
Wow, that's fantastic! Going from 23 to 58 in just 3 months is an incredible improvement. We're thrilled to hear that Bio-Avail D3/K2 is working so well for you! Thank you for sharing these objective results—it really helps others understand how effective the right supplementation can be for vitamin D levels.
We appreciate you being part of the Adapt Naturals community! Take good care!
I love it! Easy to use and my Vit D numbers have gone up, so I'm very happy!
Hi Jenifer,
That’s fantastic! We’re so glad it’s helping bring your vitamin D levels up—thank you for sharing!
I think I received a bad batch of the Vitamin D drops. It tasted rancid and unusable. There was a delay in shipping with DHL, that may or may not have contributed.
Hi Seth,
We’re so sorry about your experience—and we take issues like this very seriously. Delays in shipping can sometimes affect sensitive ingredients like the MCT oil base, but this shouldn’t have happened. We sent you a replacement and if you wouldn't mind, when it arrives, use the box it comes in and the label sent to your email to return the other one to us to help us with our investigation. We appreciate your help as we do not want it to ever happen again. Thank you!
Love this product so much! For one, the quality is amazing and two, the amount of servings you get from ONE bottle. Black women tend to have a vitamin D deficiency which is very detrimental to our overall health and mood. Working in an office all day and having darker skin can highly contribute to this. Anyways, I love this product so far. It helps so much with keeping my hair stronger, energy up and my mood more positive! I also love how you don't need 10-12 drops for a serving like other brands which makes you have to refill more often. 10/10 recommend and I will be buying this brand from now on. Highly impressed by all of my Adapt Naturals products including this one!!!
Hi Victoria,
Thank you for this thoughtful and powerful review—we’re honored that Bio-Avail D3/K2 is making such a difference in your routine. We're also big believers in making dosing easy and efficient—so we're glad you appreciate that too!
I naturally have low vitamin D levels because I don't get much sun. This product has kept me in the good zone based off my lab numbers.
Hi Donnell,
Thank you for this encouraging review! Vitamin D is essential for so many functions, from bone health to immune support, and pairing it with K2 helps ensure it’s effectively absorbed and directed to where it’s needed most. We’re so glad it’s keeping your levels in the optimal range!