Does the amount of water really matter when taking L-thyroxine?

Women with Hashimoto’s take L thyroxine daily to stabilize their thyroid function. Many women with Hashimoto’s take L thyroxine every day to support stable thyroid function. The dose appears correct, the medication is taken regularly, and yet TSH levels continue to fluctuate.

In my practice, I repeatedly see how frustrating this situation can be. This makes a clinical observation all the more interesting, as it highlights a very simple influencing factor: the amount of water used to swallow the tablet.

Water Intake and L Thyroxine: What Was Studied?

Over a longer period of time, 35 patients with Hashimoto’s who were taking L thyroxine were monitored. The following parameters were observed:

• TSH levels
• TPO antibodies
• the required dose per kilogram of body weight

Participants took their L thyroxine in the morning on an empty stomach. It was important that the tablet was taken with no more than a small sip of water, meaning less than 50 milliliters [1]. In addition, a gap of at least 30 to 45 minutes before breakfast was maintained. Coffee, milk, juice, and smoking before eating were not permitted.

The Results of the Changes

After an average of around 21 months, clear changes were observed. TSH levels decreased significantly. TPO antibodies also declined. It was also noteworthy that many patients were well adjusted with an average dose of about 1.0 microgram per kilogram of body weight. In the literature, a requirement of approximately 1.6 micrograms is often cited.
For clinical practice, this may mean that some women require less L thyroxine if absorption in the body functions optimally.

Why Might Less Water Be Helpful?

Levothyroxine must first dissolve sufficiently in the stomach before it can be absorbed in the small intestine. This process requires an acidic environment.

Larger amounts of water can dilute gastric acid. The pH value rises slightly. As a result, the tablet may dissolve more slowly, and intestinal absorption may be reduced.

Especially in Hashimoto’s, additional factors that influence stomach acid are often present:

• chronic gastritis
• Helicobacter pylori
• use of proton pump inhibitors
• reduced gastric acid production

I personally find this connection particularly relevant, as many patients with Hashimoto’s also suffer from digestive complaints. This is an area where it is worth taking a closer look.

Practical tips for taking L-thyroxine

For many patients, the following points may be helpful:

• Take it in the morning on an empty stomach.
• use only a small amount of water
• wait 30 to 45 minutes before eating breakfast.
• avoid coffee, dairy products and supplements during this time.

These recommendations do not replace individualised medical supervision. However, they may offer a simple approach to achieving stable thyroid levels when therapy is not working.