Levothyroxine: Treating an underactive thyroid

March 24, 2022
5 minute read

In the second entry of our blog series on hypothyroidism, we’ll discuss the primary way in which this condition is treated, namely by replacing missing hormone levels with the medication levothyroxine.  

If you’re not familiar with hypothyroidism, we recommend reading the first blog which provides a comprehensive overview of the condition, including causes, symptoms, and ways to get your thyroid health checked: Underactive thyroid: Symptoms and causes.

What is levothyroxine?

Hypothyroidism is a common condition consisting of thyroid hormone deficiency.  Hypothyroidism is easily diagnosed via a blood test by your GP, however, can be potentially fatal in severe cases if left untreated.

The primary treatment for hypothyroidism consists of thyroid hormone replacement therapy with levothyroxine. Levothyroxine is a synthetic version of thyroxine that can replace missing levels of thyroxine in the body.  

When administered, levothyroxine mimics the action of thyroxine, and is an effective treatment for hypothyroidism, helping to prevent the occurrence of any negative symptoms.  

What to expect from levothyroxine treatment

Before starting treatment with levothyroxine, your GP will want to do blood tests to assess your current levels of thyroxine.  

Once you begin to receive levothyroxine, more regular blood tests are required to help your GP understand if you are receiving the correct dose of levothyroxine and to make any adjustments if required.  

Generally, you’ll start on a low dose of levothyroxine, which will then gradually be increased as your GP observes how your body responds to the medication. Some individuals will start to notice a rapid improvement, while for others it may take several weeks or even months to achieve a robust improvement in their symptoms.  

Once the correct dosage has been identified, you’ll keep taking it regularly (in most cases daily), and you’ll receive a blood test once a year to monitor your hormone levels. The optimal dose for adults falls in the range of 1.5 – 1.8 micrograms of levothyroxine per kg of bodyweight.  

How to take levothyroxine

Levothyroxine is usually taken in a single dosage, at the same time every day, generally in the morning.  

It’s recommended that you take levothyroxine on an empty stomach, as food and drinks can interfere with its absorption. After taking the dosage, you should avoid eating or drinking anything else other than water for the next 30 minutes.  

You’ll have to continue treatment for the rest of your life, as hypothyroidism is a lifelong condition. It’s important to be aware that stopping treatment will mean that your symptoms will return.  

The dosage that you will be prescribed will vary from one person to another, though most adults will start with a dosage between 25 and 100 micrograms, which will then be gradually increased until your thyroxine levels are optimally replaced.  

Side effects of levothyroxine

Levothyroxine doesn’t usually come with side effects, as it’s simply replacing a hormone in your body. On some occasions, however, you may experience side effects if you’re taking too much levothyroxine.  

Symptoms of taking too much levothyroxine include:

  • Sweating  
  • Chest pain  
  • Headaches  
  • Diarrhoea  
  • Vomiting  

These symptoms coincide with the symptoms of an overactive thyroid.  

For more information on levothyroxine, including common interactions with other medicines and guidelines for taking levothyroxine in pregnancy and breastfeeding, please refer to the official NHS article:  Levothyroxine.

Please get in touch with us today if you would like to speak with one of our pharmacists.

Content last reviewed on:
March 24, 2022
Next review date:
March 24, 2024
Further reading
Patient receiving delivery from Phlo

Join our pharmacy revolution

There’s no better time to become part of the Phlo community. Take control of your medication management and join the 1,000s of patients we’ve helped safely manage their medication.

Download the Phlo app and enjoy an enhanced experience!
Link to download app from Apple StoreLink to download app from Google Play store