Iron bisglycinate and Levothyroxine: interaction, severity and spacing
Iron bisglycinate and Levothyroxine interact because iron forms insoluble chelates with levothyroxine in the gut, sharply reducing how much thyroid hormone is absorbed and destabilising TSH. Take them 4 hours apart. Severe risk.
The interaction in detail
| Pair | Iron bisglycinate and Levothyroxine |
|---|---|
| Type | Nutrient–drug interaction |
| Severity | Severe |
| Required spacing | 4 hours minimum |
| Onset | At the time of dosing |
Mechanism
Iron forms insoluble chelates with levothyroxine in the gut, sharply reducing how much thyroid hormone is absorbed and destabilising TSH.
What to do
Take levothyroxine first thing on an empty stomach, then wait at least 4 hours before iron.
How to fit both into one day
Non-heme iron absorbs best on an empty stomach with vitamin C. Coffee, tea and calcium can halve absorption, so keep them two hours away.
Levothyroxine needs an empty stomach and gastric acid for full absorption. Take it 30-60 minutes before breakfast with plain water, and keep calcium, iron and coffee at least 4 hours away.
Putting Iron bisglycinate in the morning and Levothyroxine in the morning satisfies the 4-hour separation without disrupting either one's absorption window.