Calcium (citrate): evidence, dose and safety
Calcium is the main mineral in bone, found in dairy, fortified plant drinks, tofu set with calcium and leafy greens. We use calcium citrate, which can be taken with or without food.
At a glance
- Strongest evidence
- B Good
- Dose in our plans
- 500 mg a day for adults
- Adult upper limit
- 2500 mg a day from food and supplements together
- Safety checks
- 2 situations and 6 medicine or supplement interactions, checked against your answers in every plan
- Reviewed
- Atrum Labs clinical team (MD, PhD), November 2026
Authorised EU health claim
Calcium is needed for the maintenance of normal bones.
What the research looked at
Each line is one body of research, graded A (strong) to D (weak). How we grade evidence. What each study measured is explained in your personal plan.
| Grade | Who was studied | References |
|---|---|---|
| B | People with low dairy intake |
|
How much
- Our plans usually use 500 mg a day for adults. The exact dose depends on your lab results, age and medicines.
- Adult upper limit: 2500 mg a day from food and supplements together. Source: EFSA 2012 calcium UL.
- Children's doses are set by age, and some ingredients are for adults only.
Who should not take it, or should check first
- A clinician checks first. Supplemental calcium (not dietary) may raise stone risk.
- Not suitable. Serum calcium is already raised; more calcium would make it worse.
Medicines and other supplements
- Take with care. Take calcium at least 4 hours apart from levothyroxine.
- Take with care. Calcium binds quinolones and tetracyclines. Take ciprofloxacin at least 2 hours before or 6 hours after it (moxifloxacin 4 and 8 hours; tetracyclines 2 to 3 hours apart).
- A lower dose is used. Thiazides reduce calcium excretion; hypercalcemia (milk-alkali) risk.
- Take with care. Calcium stops oral bisphosphonates being absorbed. Take the bisphosphonate on waking with water, at least 30 minutes (ibandronate 60) before this sachet, any food or other medicine.
- A clinician checks first. Calcium lowers levels of HIV integrase inhibitors (dolutegravir, bictegravir, raltegravir), which risks treatment failure and resistance. Timing must follow the HIV medicine's label.
- Take at a different time. Calcium reduces non-heme iron absorption.
Your plan is checked against every medicine you tell us about. If you take a medicine, ask your pharmacist or doctor before starting a new supplement.
Written and reviewed by the Atrum Labs clinical team (physician-scientists, MD, PhD) from our clinical knowledge base, version 0.2.0-draft. This page is general information, not medical advice. Food supplements are not a substitute for a varied, balanced diet and a healthy lifestyle.
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