Thyroid medicine can be affected by

thyroid medicine can be affected by

Thyroid medicine

The type of thyroid medicine I will be discussing is the one used for hypothyroidism where levels of thyroid hormone in the body are low and need to be increased.  There are a couple of other medical conditions where thyroid hormone medicines are taken.

The name of thyroid hormone medicine is thyroxine (sometimes called levothyroxine).  Thyroxine is best taken first thing in the morning and so other medicines should be timed around this.


Thyroxine and calcium/dairy products

Calcium, present as a supplement or in dairy products, can latch on to thyroxine and stop it from being taken in by your body.  This means that levels of thyroid hormone in the body will get lower.  Calcium supplements are best taken at night so if you need to take calcium take it at this time.  If you want to consume dairy in the morning you should wait until at least two hours after taking thyroxine to do this.


Thyroxine and iron supplements

Iron is a mineral that significantly lowers the amount of thyroxine that is absorbed if they are taken together.  It is important to take iron at lunch time or even dinner time if you also take thyroxine so that there is a gap of at least four hours between taking them.


Thyroxine and food

Eating at the same time as taking thyroxine lowers the amount of thyroxine absorbed.  Take thyroxine first thing in the morning and don’t eat for at least half an hour to avoid this problem.

High fibre foods such as cereal should be consumed two to three hours away from thyroxine as these can have more of an effect.

Cruciferous vegetables such as broccoli and cauliflower can lower thyroid hormone levels in the body.  It is best to keep a consistent intake of these vegetables.  That means to have a little bit each day or every second day so that the effects of these healthy foods are balanced out.


Thyroxine and soy (eg tofu)

Soy can decrease thyroid hormone levels in the body.  If you use soy you may need a higher dose of thyroxine.


Thyroxine and multimineral supplements

Essential trace minerals need to be separated from thyroxine use by four hours.  Lunch or dinner time is a good time to take these supplements which are quite commonly needed in those with a thyroid hormone deficiency.




If you have been taking thyroxine for a while and have it, for example, with food and supplements don’t change what you do all of a sudden.  The dose of thyroxine that you take will be based on blood tests and the effects of interfering food and medicines will be reflected in your dose.

Speak with your Pharmacist or Doctor before you change how you take thyroxine.





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