How antibiotics impact thyroid hormone production

What to know when taking antibiotics while having an underactive thyroid or Hashimoto’s

Antibiotics are great, and they’re the most effective way to combat bacterial infections — but they can cause some side effects.

Some of the more known side effects are changes in the bacterial composition of the gut, which can cause a lot of problems to anyone, but especially to people with thyroid issues.

For people with thyroid problems, another side effect of some antibiotics includes reduced effectiveness of zinc. Zinc is a metal necessary for proper functioning of almost all the cells in the body.

Similar to selenium, zinc is necessary for the production of thyroid hormones in the body (1). If there’s not enough zinc, there will not be enough thyroid hormones — leading to an underactive thyroid.

The body has no specific storage for zinc, so it has to be taken on a daily basis to keep levels up (2). There are many zinc supplements, and the best ones are zinc bound to amino acids: aspartate, cysteine, and histidine (3).

The connection between zinc and thyroid hormones is more complicated: right amounts of thyroid hormones are necessary for the body to uptake enough zinc in the gut from the foods or supplements.

Zinc as the immune system defender

Zinc is especially important for protecting lungs and the stomach — organs exposed to a lot of viruses and bacteria, and zinc makes it possible for the cell membrane to stay intact (4).

The immune system is specifically sensitive to low zinc levels, in fact around the globe low zinc levels are the cause for 2 in 10 of respiratory infections and 1 in 10 diarrhea problems (5).

Zinc blocks inflammation in the body (6), and is necessary for regulation of a process called apoptosis — aka programmed cell death — which is a healthy process in the body. However, this process is broken in people with autoimmune diseases (7).

Taking antibiotics with an underactive thyroid

Having an underactive thyroid and taking antibiotics can sometimes cause a spiral—ending up with both low zinc and thyroid levels (8). It might take some weeks for symptoms to resolve after you’ve completed your course of antibiotics.

Azithromycin (Zithromax®) and clarithromycin (Biaxin®) are known to cause zinc issues.

How do you know your zinc levels are low?

  • Bitter taste in the mouth

  • Sudden hair loss

  • Feeling depressed

  • Prolonged bouts of diarrhea

  • Delayed wound healing

Currently there is not standard recommendation of the amount of zinc supplementation to take — there are many opposite research findings, but it’s known is that zinc deficiency will cause multiple problems with health, and that people with an underactive thyroid might be more sensitive than the general population.

It’s best to talk to your health care practitioner about the most recent health guidelines and zinc supplementation.


1. Vallee BL, et al. The biochemical basis of zinc physiology, 1993

2. Mills CF. Zinc in Human Biology, 2013

3. Brieger A, et al. Zink und Immunfunktionen, 2013

4. Gammoh NZ, et al. Zinc in Infection and Inflammation, 2017

5. World Health Organisation . The World Health Report. World Health Organization; Geneva, Switzerland: 2002.

6. Prasad AS, et al. Antioxidant effect of zinc in humans, 2004

7. Truong-Tran AQ et al. The role of zinc in caspase activation and apoptotic cell death, 2001

8. Ambooken B, et al. Zinc Deficiency Associated with Hypothyroidism: An Overlooked Cause of Severe Alopecia, 2013