What do the states mean?+
- Solid: well studied, and it works.
- Half-there: the science is still forming.
- A ghost: almost no real studies.
- Hollow: well studied, and it does not work.
- A cord: the pair itself has been tested together.
- Air: nobody has ever tested this pair.
The full scoring method: How we score
Can you take calcium and vitamin K2 together?
Take them together.
As of August 2026, calcium and vitamin K2 have been tested together in 10 trials, and the pair came out ahead of taking either alone. Scored under the same rules as everything here.
42 studies · 10 tested the actual pair
What you’re seeing
- Calcium renders hollow: for bone, it is well studied and it does not work.
- Vitamin K2 renders half-there: for bone, the science is still forming.
- The woven cord is the rare part: ten trials gave both together, and the pair came out ahead of taking either alone.
You can tell before you read a word.
Magnesium + L-theanine are sold together in the same aisle. No trial has ever tested the pair. When that is true, we draw nothing between them. The nothing is the review.
The pooled pair trials
- 2021Meta-analysis · 1,346 people · adults in trials of vitamin K with calcium for bone density · the pair helpedsource
The other 32 studies on file tested each one alone. See all 42 studies
Fair questions
Is it safe to take calcium and vitamin K2 together?+
The studies on this page gave both together and reported no harm from the combination. That is not the same as a safety trial, and it says nothing about your dose or your medication.
How many studies is this based on?+
1 that gave the pair together. The papers are listed above with links to the source.
Deeper
What each one is on its own+
Calcium
- Bonehollow
- Pregnancyhalf-there
Vitamin K2
- Bonehalf-there
- Blood sugarhalf-there
- Cholesterolhollow
- Hearthalf-there
- Inflammationhollow
- Moodhalf-there
- Strength and powerhalf-there
Pairs that have been tested+
- Calcium has been tested with magnesium, vitamin D, probiotics, kava.
- Vitamin K2 has been tested with vitamin D.
These are the combinations someone has actually run a study on. Every other pairing here is air.