Thyroid UK
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Drugs/food and drink that interfere with Levothyroxine Absorption

Interactions that result in reduced levothyroxine absorption:


calcium carbonate (TUMS)

calcium carbonate and magnesium hydroxide (ROLAIDS)


aluminum hydroxide (AMPHOJEL)

iron supplements

ferrous sulfate (FEOSOL, SLOW FE)


cholesevelam (WELCHOL)


raloxifene (EVISTA)**

sevelamer (RENAGEL, RENVELA)

sucralfate (CARAFATE)**


ciprofloxacin (CIPRO)

levofloxacin (LEVAQUIN)**

lomefloxacin (MAXAQUIN)**

moxifloxacin (AVELOX)*

norfloxacin (CHIBROXIN, NOROXIN)**

ofloxacin (FLOXIN)**

Grapefruit Juice

Interactions that result in increased levothyroxine metabolism, lower levels of in the blood


carbamazepine (CARBATROL, TEGRETOL)

oxcarbazepine (TRILEPTAL)

phenobarbital (LUMINAL, SOLFOTON)**

phenytoin (DILANTIN)

primidone (MYSOLINE)


efavirenz (SUSTIVA)

nevirapine (VIRAMUNE)

rifabutin (MYCOBUTIN)


St. John’s wort


imatinib (GLEEVEC)

sertraline (ZOLOFT)**

Interactions that result in changes of levothyroxine binding in blood


Interaction that results in increased or decreased levels of other drugs

warfarin (COUMADIN)

8 Replies

Must say I've never heard of half those drugs.

Add tea to the list.

This is why this TUK recommends taking thyroid medication at least an hour away from meals with just water, as tea, dairy products, iron and fluoride all interfere with it.

1 like

You can also add milk to the list which is fortified with calcium. Didn't realsied how much until my endo told me not to have milk anywhere near my levo.

Moggie x


I think that is the easiest mistake in the world to make when taking levothyroxine in the morning. Then breakfast - quite likely cereal with milk, coffee or tea with milk, yoghurt, or some other form of milk.

Also some cereals, such as Special K, are fortified with iron.



That's true but I guess like taking the contraceptive pill daily, as long as you have the same amount of milk every morning and your blood test results take this in account its fine to take in the morning


But how many really do have the same amount of milk every morning?

Lots of people change their breakfast at weekends, on holiday, if they oversleep, when attending a course, when they are ill, dieting to lose weight, ...

There are many possible reasons for the absorption to vary when taken in conjunction with food.



thanks for the info I find this list very helpful but please be aware also of some dressings which contain iodine, I had a trip to A&E for a cut hand they wanted to put an iodine dressing on my hand which was a big no no


There is a whole chapter of Thyroid Manager on this sort of thing:

As always with the site, not easy reading.



I know this is a UK board, and I am a American, but this effects all people.

Add Levsin S/L colon spasm drug to the list, it makes your Synthroid run HOT. Why is it ENDO's don't give patients at least nutrition facts or most common drugs/supplement lists when they are being treated for Hypothyroidism. First thing they do with a diabetic is send them to nutritionist training. I have new internist, his knowledge of Thyroids would fit in a thimble a small 1 @ that. I did not know he was running T Panels until Jan, when the nurse calls and says your T panel is running hot. & he wants a Radioactive Thyroid Scan. ALL warning alarms go off. I'd just told him I saw the Endo in March. Having no issues with my med. After 1 bad reading you who have never asked 1 question, or felt my Thyroid want to run this dangerous test? When you know I have an ENDO and I have a very injured neck that will not heal nor will Neurosurgeon repair. He also wrote a pain script for NARCO it is going to replace Lore Tabs, less Tylenol, more severe side effects, addictive too. Has a clear warning DO NOT GIVE TO THYROID patients. 1 pill sick in 10 mins, lasted 3 days. Took me 1 minute to find the culprit as it is the only new drug or supplement I was on. LEVSIN S/L for colon spasms, I'd had a severe colon infection that had me hospitalized in Oct,


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