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 vitamin D and iron together?
You don’t need to take them together.
As of August 2026, vitamin D and iron have been tested together in 1 trial, in women aged 18 to 45 with low haemoglobin and low vitamin D, and no clear added effect was found. Scored under the same rules as everything here.
6 studies · 1 tested the actual pair
What you’re seeing
- Vitamin D renders hollow: for bone, it is well studied and it does not work.
- Iron renders solid: for anaemia and iron levels, it is well studied and it works.
- The woven cord is the rare part: one trial gave both together, and no clear added effect was found.
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 pair trial
- 2021Randomized trial · 87 people · women aged 18 to 45 with low haemoglobin and low vitamin D · no clear effectsource
The other 5 studies on file tested each one alone. See all 6 studies
Fair questions
Is it safe to take vitamin D and iron 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.