Ramadan fasting and the thyroid

Ramadan moves 11 days every year — an Islamic year has 354 days, as the Islamic calendar is based on the lunar cycle. This month of fasting may fall during any of the four seasons, so the duration of daily fasting ranges from 11 to 18 hours depending on the season and where you live (2).

Prolonged fasting during Ramadan might cause some minor metabolic and hormonal changes in the body — this can affect thyroid gland activity (1).

Ramadan fasting is different from intermittent or other types of fasting, as drinking is not permitted during the fasting periods between sunrise and sunset. The majority of people participating have two average sized meals per day — one immediately after sunset (Iftar), one just before dawn (Sehur).

Ramadan fasting effects on the thyroid

Any type of fasting is associated with (2–5):

• A slowdown in T4 to T3 conversion rates
• Lower T3 levels
• Increased rT3 levels

Thyroid hormone levels usually return to normal after fasting (3–5).

Research has shown that females have lower tT3 levels after 30 days of Ramadan fasting — there were no T3 effects in males (6–8). However, both females and males might experience an increase in TSH levels (9).

Levothyroxine and Ramadan fasting

Synthetic T4 hormone — which is taken daily as a pill — is better absorbed into the bloodstream while fasting compared to non-fasting periods (10, 11). Yet this might cause temporary symptoms of overtreatment, including shaky hands (tremor), heart palpitations, excessive sweating, and faster digestion (9–11).

The eating scheduling during the month of Ramadan causes changes in gastric motility and circadian rhythm. This might affect deiodinase activity (enzymes that convert T4 into T3), which can cause low T3 levels and symptoms including fatigue and brain fog (12, 13).

When should you take levothyroxine while fasting during Ramadan?

Recommended options for taking levothyroxine for people with hypothyroidism (2):

• One hour before Iftar (meal eaten after sunset)
• One hour before Sehur (meal eaten before dawn)
• Four hours after Iftar

However, this can be difficult because it might interfere with sleeping routines.

You should wait at least two hours after eating your last meal if you decide to take your dose at bedtime (13–15).

Special cases during Ramadan fasting

Pregnant people, people over 65, and people with osteoporosis should be monitored frequently as their TSH levels significantly impact their health (13).

How we write: our information is based on the results of peer reviewed studies using the National Library of Medicine platform. It is written by scientists and reviewed by external experts. If you believe we might have overseen crucial scientific information, please contact us at hello@boostthyroid.com

Disclaimer: This information is not intended to mitigate, prevent, treat, cure or diagnose any disease or condition. If you want to change your treatment, lifestyle, your diet, include supplements in your diet or have concerns about your health, please consult your doctor before trying new approaches.

References:

1. Ziaee V, et al. The changes of metabolic profile and weight during Ramadan fasting, 2006
2. Azizi F. Islamic Fasting and Thyroid Hormones, 2015
3. Portnay GI, et al. The effect of starvation on the concentration and binding of thyroxine and triiodothyronine in serum and on the response to TRH, 1974
4. Spaulding SW, et al. Effect of caloric restriction and dietary composition of serum T3 and reverse T3 in man, 1976
5. Carlson HE, et al. Alterations in basal and TRH-stimulated serum levels of thyrotropin, prolactin, and thyroid hormones in starved obese men, 1977
6. Azizi F, et al. Evaluation of certain hormones and blood constituents during Islamic fasting month, 1986
7. Sulimani RA. The effects of Ramadan fasting on thyroid functions in healthy male subjects, 1988
8. Bahrayni SH, et al. The effect of Ramadan fasting on thyroid hormones in 9–13 years old pre-menarche girls, 2013
9. Azizi F. Effect of dietary composition on fasting-induced changes in serum thyroid hormones and thyrotropin, 1978
10. Fish LH, et al. Replacement dose, metabolism, and bioavailability of levothyroxine in the treatment of hypothyroidism, 1987
11. Biondi B, et al. Treatment with thyroid hormone, 2014
12. Raza SA, et al. Thyroid diseases and Ramadan, 2012
13. Koca AO, et al. Should the dose of levothyroxine be changed in hypothyroidism patients fasting during Ramadan, 2020
14. Karoli R, et al. Levothyroxine replacement and Ramadan fasting, 2013
15. Sheikh A, et al. Impact of Ramadan fasting on thyroid status and quality of life in patients with primary hypothyroidism: a prospective cohort study from Karachi, Pakistan, 2018

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