What time should I take my Levothyroxine?

Despite levothyroxine being the treatment of choice for those with an underactive thyroid there are few guidelines in term of timing.

Patients are usually advised that the drug should be taken on an empty stomach and preferable 30 minutes before breakfast.  But for some people this is tricky, particularly when they may be on several other medications requiring similar restrictions.

Some studies suggest that it’s actually the length of time before eating which is more important than the time of day it is taken.

Might thyroid hormone levels be optimised by taking levothyroxine just before bed on an empty stomach?

A trial involving 90 patients with primary hypothyroidism saw them receiving levothyroxine either in the morning or in the evening with a switch after three months.

Results showed that taking Levothyroxine at bedtime actually improved thyroid hormone levels compared to taking it in the morning.  There was a reduction in serum thyrotropin (TSH) of 1.25 mIU/L and small increases in free thyroxine (T4) and total triiodothyronine (T3) concentrations.

Whether such small changes in serum TSH have any clinical impact in patients on levothyroxine is still uncertain. Despite the change in thyroid hormone levels, the patient quality of life and other secondary outcomes didn’t differ and it’s possible that a longer duration of study is required to demonstrate any benefit.  

However, bedtime levothyroxine intake may be more convenient for patients and will therefore enable greater compliance.

If a dose is missed on one day you can always take double the dose the next day. If you take double the dose one day you can miss the dose the following day.

In summary it is advised to take levothyroxine on waking with a glass of water half an hour before breakfast to maximize absorption. In some people the timing may not be so important and the key thing is remembering to take the dose daily.