Levothyroxine sodium (or thyroxine) is the most commonly prescribed thyroid hormone replacement medication in Australia. Many Hashimoto’s or post-thyroidectomy patients take thyroxine on a daily basis, to ensure healthy thyroid hormone levels. That said, it’s well-recognised that many drugs, foods and nutrients interfere with the absorption of thyroxine, and for this reason, most patients are instructed to take their thyroxine first thing in the morning, at least 30-60 minutes before any food or drinks. But is first thing in the morning really the best time to take your thyroid medication? The answer is, it really depends - let’s explore a little deeper!

Why Does Thyroxine Need to be Taken on an Empty Stomach?

As mentioned above, thyroxine absorption can be impacted by many things, such as food, nutritional supplements and other medications. Certain supplements, such as calcium tablets, antacids and iron supplements have such a strong effect on thyroid hormone absorption that you should wait at least 2-4 hours between taking your thyroxine and using these agents. Not doing so can impair thyroxine absorption by up to 50%, meaning you might need a higher dose to maintain healthy thyroid hormone levels. Other substances well-known for their inhibitory effect on thyroxine absorption include cow’s milk, coffee, tea, soy, fibre supplements, magnesium supplements, sucralfate, cholestyramine and grapefruit juice. Many of these substances bind with thyroxine, preventing it from diffusing across the gut wall and into the blood. A common situation I see in clinic is patients who are unintentionally reducing their thyroxine absorption by taking their tablet with a cup of tea!

The Standard Recommendations

The standard recommendation is to wait at least 30-60 minutes between taking your thyroxine and consuming any food, drinks or other supplements/medications (with the exception of water). Typically, thyroxine has a bioavailability of around 40-80% when taken under these conditions (some reports suggest up to 70-80%), however absorption may decrease with age and in those with compromised digestive function. Again, for certain substances, you need to wait longer - for example, with antacids, calcium supplements, iron supplements and/or magnesium supplements, you need to take your thyroxine at least two hours before or four hours after these supplements.

Whilst the standard recommendation is 30-60 minutes before food, many of my patients have been able to reduce their dose of thyroxine (with their doctor’s supervision) by waiting at least one-and-a-half to two hours between taking their medication and having breakfast. This allows more time for the thyroxine to be absorbed, unaffected by other substances in the digestive tract (theoretically enabling a greater percentage of the medication to be taken up into the blood). Of course, this approach doesn’t work for everybody, especially if they have limited time in the morning, can’t take their breakfast to work, or if they feel too hungry to wait so long. In such cases, we might consider some of the other alternatives, which I’ll discuss below.

Other Options

The aim of taking thyroxine in the morning is to maximise your absorption of the drug, whilst also maintaining steady thyroid hormone levels by taking the medication under the same conditions each day. This means if you choose to take it at another time of day, you should do so under the same conditions every day.

Bedtime Dosing

For example, some patients find it easier and more convenient to take their thyroxine at bedtime, ideally at least three to four hours after their last meal. Many patients report feeling better when taking their thyroxine at bedtime, and appreciate the convenience of not having to wait for their morning coffee! This can also be a good option for patients who have to take other medications early in the morning. In fact in one study, published in the Archives of Internal Medicine, bedtime administration of thyroxine significantly improved thyroid hormone levels, compared to morning dosing. Although this was a relatively small pilot study, the results were definitely encouraging, so hopefully more research will be done in future. Other studies (as summarised in this Medscape article) have found no difference between morning or bedtime dosing. That said, if you feel you are not benefitting from the full dose of your thyroxine in the morning and don’t take any medications at nighttime, a bedtime dosing regime might be something worth exploring with your doctor.

Early Morning Dosing

Another option for patients with regular nighttime bathroom habits might be to take their thyroxine when they wake to go to the bathroom (e.g. around 3 or 4 AM). This may be a good option for you if you consistently wake around the same time every night and will remember to take your thyroxine in your half-asleep state. By taking your thyroxine at 4 AM and then heading back to bed for a couple hours before breakfast, you easily give your body a couple extra hours to absorb the medication. A number of my patients have adopted this approach (with their doctor’s permission) and have even been able to reduce their thyroxine requirements by doing so. Importantly, this option does not work for patients who do not wake up every night, as they might accidentally skip a dose. For patients who always go to the bathroom at night but are worried they might forget whether they’ve taken their dose, I recommend using a pillbox, so that it is abundantly obvious in the morning whether you took the dose or not. That said, I do not recommend setting an alarm in the middle of the night to take your thyroxine, as this can be very disruptive to sleep and overall wellbeing.

The Take Home

Ultimately, the best time to take your thyroxine is determined by many factors, such as your breakfast habits, working arrangements, other medication requirements and compliance. If you have plenty of time in the morning, don’t take other morning medications and can delay your breakfast an hour or so, it is likely that morning dosing will be the easiest option for you. If you often forget to take your thyroxine in the morning, need to have breakfast early or take other medications early in the day, you might benefit from a bedtime dosing regime. Overall, it’s best to consider these different factors with your healthcare provider and determine a dosing regime that is most suitable for you, your individual circumstances and your response to thyroid hormone replacement therapy.

Note

If you’re considering changing the time of day you take your thyroxine, it’s important to discuss this with your doctor or endocrinologist first, to ensure appropriate follow-up monitoring of your thyroid hormone levels is conducted.
In general, it is recommended follow-up thyroid hormone testing is performed 6 weeks after a change in medication dose or schedule, to assess the effect.
This article is not intended to serve as medical advice, nor replace the professional opinion or recommendations of your doctor or endocrinologist.