Informational Posts

Caffeine and Your Thyroid

Caffeine and Your Thyroid
Originally published on 10th October 2016
Last updated on 22nd May 2019

If you have thyroid issues (especially Hashimoto’s), adrenal fatigue, insomnia or trouble sleeping, anxiety etc. it’s important to be aware of the impact of caffeine.

It Can Affect How Much of Your Thyroid Medication You Absorb

It’s well reported, that caffeine impacts the absorption of T4-only thyroid medication such as Levothyroxine, which is why thyroid patients need to wait at least an hour after taking their T4 medication before drinking any tea or coffee. [1]

I personally would avoid all caffeine within an hour of taking any thyroid medication, not just Levothyroxine, to be on the safe side. To get around this, an option could be to take levothyroxine medication at night. Some studies have shown that taking levothyroxine at bedtime may improve absorption. It also allows for you to have your morning cup of coffee without worrying about it affecting your thyroid medication. [2]

It Can Increase Blood Sugar

Caffeine heavily increases our blood sugar levels when consumed.  Blood sugar spikes cause cortisol to shoot up, which can tire out the adrenals and exacerbate hypoglycaemia, Hashimoto’s and ‘adrenal fatigue’. [3]

I have covered in another post why so many of us with thyroid problems are likely to suffer from blood sugar imbalances, so this is a serious thing to consider and explore. If you get ‘hangry’ (hungry and angry), dizzy, faint and irritable when hungry, you could well have blood sugar imbalances.

It Can Tire Out Your Adrenals

As touched on above, caffeine makes our blood sugar spike, which causes the adrenal glands to pump out more cortisol. Also, when your blood sugar levels drop below normal, sometimes after a spike, your adrenal glands respond by secreting more cortisol. This cortisol then tells the liver to produce more glucose, which brings blood sugar levels back to normal. Doing this repeatedly can cause abnormal cortisol output and can suppress pituitary function. [4]

Drinking a lot of caffeine whilst also having ‘adrenal fatigue’ (note: it is more accurately referred to as hypothalamic-pituitary axis dysfunction) adds fuel to the fire and can make it worse.

It Can Damage The Gut Lining and Encourage Acid Reflux

Coffee can irritate the oesophagus or weaken the lower oesophageal sphincter, which prevents the backward flow of stomach contents that causes acid reflux.

Coffee is highly acidic, so it stimulates the release of gastrin and bile. For people with autoimmune conditions, compromised digestion (such as IBS or leaky gut), this can cause further digestive damage to the intestinal lining. This may not be great for your gut health which is so intertwined with thyroid health and function. Many of us with thyroid conditions also have poor gut health.

It Can Cause Migraines

Caffeine can trigger or contribute to migraines and headaches.

Since caffeine narrows the blood vessels that surround your brain, when you stop consuming it, they expand again, and this can cause pain.

It’s easy for your body to get used to caffeine, and when you don’t have it in your system, you can have a withdrawal headache or migraine. You may have a few cups a day at work, then on the weekends don’t drink any, and experience caffeine withdrawal headaches or migraines. This is a sign of dependency.

As explained above, the spike in blood sugar caused by caffeine, could also cause headaches.

Some women experience migraines around the time of their period, possibly because of changes in the level of oestrogen and progesterone, and as the below explains, caffeine may affect oestrogen levels too.

It May Contribute to Too Much Oestrogen

Studies have shown that women who consumed at least 500mg of caffeine daily, the equivalent of four or five cups of coffee, had nearly 70% more oestrogen than women who consumed no more than 100mg of caffeine daily (less than one cup of coffee). Tea contains about half the amount of caffeine compared to coffee.

Migraines, heavy periods, PMT, acne and even breast cancer can be symptoms of too much oestrogen.

We are told that oestrogen dominance inhibits T4 to T3 conversion, which can be a reason why your thyroid medication doesn’t seem to be reducing thyroid symptoms.

However, whether this condition really exists is still debated. Read more here.

It Can Contribute to Insomnia and Poor Sleep

A study showed that 400mg of “caffeine taken 6 hours before bedtime has important disruptive [sleep] effects” though this can be dependent on the individual and their ability to metabolise caffeine. [5]

It is often recommend that we avoid consuming caffeine after lunch time, in order to promote a better night’s sleep.

As explained above, caffeine also often contribute to adrenal issues, and a key sign of adrenal dysfunction includes trouble getting to sleep and/or staying asleep.

All thyroid patients can benefit from going caffeine-free to see if/how it affects them.

People who give up caffeine tend to report better sleep, less headaches, fewer hot flashes, less anxiety, and less hypothyroid and digestive issues.

I realised that caffeine was contributing to my debilitating migraines, so I cut it out, and haven’t gone back since.

However, many thyroid patients also state that they feel OK consuming caffeinated tea and coffee, so it really can be individual. Caffeine is not something that usually needs to be avoided for life by most of us with hypothyroidism or Hashimoto’s. Many of us can enjoy it in reasonable amounts, though may benefit from avoiding it when overcoming adrenal issues, and reintroducing it after these are addressed.

Do you notice any link between caffeine and your health?

You can click on the hyperlinks in the above post to learn more and see references to information given.







About Author

Rachel Hill is the highly ranked and multi-award winning thyroid patient advocate, writer, speaker and author behind The Invisible Hypothyroidism. Her thyroid advocacy work includes writing articles, authoring books, producing her Thyroid Family email newsletters and speaking on podcasts and at events about the many aspects thyroid disease affects and how to overcome these. She is well-recognised as a crucial and influential contributor to the thyroid community and has a large social media presence. Her bestselling books include "Be Your Own Thyroid Advocate" and "You, Me and Hypothyroidism".


  • Annette Laney
    June 8, 2022 at 1:31 pm

    Need help in keeping my thyroid in balance

  • Anita
    August 27, 2020 at 11:38 pm

    My Dr. told me I can drink coffee, but after 1 hr. after I take my levothyroxine pill in the morning. no more than 2 cups/day.

  • Suzanne
    August 1, 2019 at 3:47 pm

    Is decaff coffee okay?! : )

    • Rachel Hill
      August 5, 2019 at 10:44 am

      It is said to be better for some things, such as adrenals, blood sugar, migraines etc. It’s really often a case of seeing if it helps in your personal experience 🙂

  • Caroline
    July 31, 2019 at 10:42 pm

    Is the caffeine in black tea the same impact on thyroid and my hashimoto as the caffeine in coffee?

    • Rachel Hill
      July 31, 2019 at 10:49 pm

      Caffeine is still caffeine, but the amounts can differ quite a bit between coffee and tea for example.

  • B Linder
    May 23, 2018 at 10:27 pm

    Very good written information. It will be valuable to anybody who employess it, as well as yours truly :). Keep up the good work – for sure i will check out more posts.

  • Tracee
    February 20, 2017 at 1:54 pm

    Can I subscribe to this ?


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