When Should You Take Your Thyroid Medication?

Readers frequently write in with thyroid-related questions. Here's a very common one, asking about what time of day is best to take your thyroid hormone replacement medication, along with some of my thoughts on the subject.

"Is it okay to take the thyroid medication the doctor has prescribed at bedtime, 2 hours after dinner, or even when I wake up in the middle of the night, around 3 to 4 am? I'm always in a rush when I get up in the morning..." -- L.R.

Dear L.R.,

You should first ask the doctor what she/he thinks about when to take your medication. But keep in mind that the studies have shown that the key with thyroid medication is taking it consistently -- taking it around the same time each day -- and in the same way (without food, or several hours apart from eating, etc.)

Research reported in the journal, Clinical Endocrinology, did find that taking the same dose of levothyroxine (i.e., Synthroid) at bedtime, as compared to first thing in the morning, might be better. (Read Should You Take Your Thyroid Medication at Night?) A small pilot study was prompted by observation that some patients had improved thyroid hormone profiles after they switched from taking their levothyroxine in the morning, to bedtime. The purpose was to look at the impact on thyroid hormone profiles by changing the time levothyroxine was taken from early morning to bedtime.

They also evaluated the impact of this change on the circadian rhythm of TSH and thyroid hormones and thyroid hormone metabolism.

The study, while small (12 subjects), was fairly conclusive in its findings, which the researchers said were "striking" and which have "important consequences for the millions of patients who take l-thyroxine daily."

Researchers reported that taking medication at bedtime, rather than the morning, results in "higher thyroid hormone concentrations and lower TSH concentrations." TSH decreased and Free T4 levels rose in all patients by changing thyroxine ingestion from early morning to bedtime and T3 levels rose in all but one subject. And TSH decreased irrespective of the starting TSH levels, suggesting better absorption of the thyroid medication when taken in the evening. Interestingly, the researchers found that the circadian TSH rhythm -- the typical daily fluctuations of TSH that occur during a 24-hour period -- does not vary.

The researchers suggested several explanations for the results:

  • Even when waiting at least 30 minutes to eat, breakfast may be interfering with the intestinal absorption of thyroid medication
  • "Bowel motility is slower at night," which means that it takes longer for the levothyroxine tablet to transit through the intestinal system, resulting in longer exposure to the intestinal wall, and therefore, better uptake of the medication.
  • The conversion process of T4 to T3 may be more effective in the evening.

The researchers have suggested that given the results of this pilot study, a large double-blinded randomized study will need to be performed to confirm their results.

Taking medication at bedtime instead of in the morning could have major implications for many thyroid patients.

  • First, it's easier, as you don't have to worry about when to eat breakfast.
  • Second, it's easier to avoid medications, supplements, and foods, like calcium, iron, and high-fiber foods that can interfere with thyroid medication absorption.
  • Third, it might offer some improvement in symptoms to people who are just not getting optimal absorption by taking thyroid medication during the day.

While this was a small study, it confirms what many patients anecdotally have been reporting for years -- that they feel better if they take their thyroid medication in the evening, rather than the morning.

You may want to talk to your practitioner about changing the time you take your medication to bedtime, versus morning. And if you decide to change to taking your thyroid medication in the evening, be sure to have your thyroid levels evaluated -- six to eight weeks is a reasonable timeframe -- after you've made the switch. The blood test results, along with any improvements or worsening of symptoms, will help you and your doctor to determine if you need to adjust the dosage or timing of your medication.

Note, however, that this study was conducted with levothyroxine -- a synthetic form of the long-acting T4/thyroxine thyroid hormone. This form of the hormone must first be converted in the body to the active form (T3) and this can take days. Thyroid drugs that contain T3 -- Cytomel, Thyrolar, and the natural desiccated thyroid drugs like Armour can by used directly by the body within hours. These drugs were not evaluated in the study.

Anecdotally, some thyroid patients have reported improvement in symptoms when taking their T3-based thyroid hormone replacement medications in the evening. But some thyroid patients also find that if they take a medication with T3 later in the day or in the evening, the slight stimulatory effect of the T3 medication can make it difficult to sleep.

So keep in mind that while it's possible that if a similar study were conducted with T3 drugs, the results would be similar, there is some chance that it would impact sleep quality. Only make such a change after discussing it with your doctor.

Optimally, some doctors have suggested that patients who take medications with T3 split their doses to take them throughout the day, leaving a dose for bedtime. This approach seems to minimize sleep interference.

Again, if you do make a change to how you take your T3 thyroid medication, you'll want to have a reevaluation of blood levels and symptoms after several weeks, to determine if you need to adjust the dosage or timing of your medication.

Ultimately, consistency is the key.

Live well,



Bolk, Nienke et. al. "Effects of evening vs morning thyroxine ingestion on serum thyroid hormone profiles in hypothyroid patients." Clinical Endocrinology 66 (1), 43–48

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