Dose timing
What to keep apart, and what spacing cannot fix
Some things genuinely just need to be taken hours apart — calcium blocks iron, and both block thyroid medicine. Others cannot be fixed by the clock at all, however carefully you space them, and being told otherwise is worse than being told nothing.
This page never tells you how much to take. Not once. When something is taken, and whether food is involved, are facts about the substance. An amount is a prescription, and that is your doctor’s to write — always follow the label on the product in your hand.
What are you taking?
This is the same list your doctor-visit report uses, so anything you add here appears there too. It stays on this device.
Add what you take above. Try levothyroxine with calcium, or an iron supplement with black tea, and you will see the difference between a clash the clock can fix and one it cannot.
How this timing guidance is calculated
- What this page shows
- Two separate things: documented absorption clashes where taking items hours apart genuinely solves the problem, and flagged interactions where it genuinely does not.
- What it uses
- Approved prescribing information for each medicine named, the NIH Office of Dietary Supplements fact sheets for the minerals and vitamins, and our own curated herb interaction table for the second list.
- How it is weighted
- Nothing is scored or ranked. Each pair is classified by how its mechanism behaves in time — binding in the gut, a liver-enzyme change that lasts days, or two things acting on the same system in the bloodstream. Only the first can be fixed by spacing, and the other two say so plainly.
- What it is NOT
- It is not a medication schedule and it is not personalised to you. It cannot see your doses, your kidney or liver function, or why each medicine was prescribed. It never states an amount of anything.
Why these factors
- Mineral and vitamin absorption comes from the NIH Office of Dietary Supplements fact sheets.
- Separation intervals come from the approved prescribing information for the medicine concerned — four hours for levothyroxine and minerals, six for the fluoroquinolones.
- Of the 38 herb–medicine interactions in our own table, not one is an absorption problem. Every one is either a liver-enzyme effect or two things acting at once in the blood — which is exactly why "just space them out" is the wrong answer for all of them.
Educational information, not medical advice. Never change when or whether you take a prescribed medicine without asking the person who prescribed it — some are deliberately timed for reasons that have nothing to do with absorption.