4 Causes of Fatigue in PCOS

1. Insulin and Glucose Balance

One of the major metabolic disruptions in PCOS is due to insulin and glucose. For example, insulin resistance can result in higher insulin levels. This in turn can disrupt the glucose balance. Specifically, glucose cannot get inside a cell to help create energy. We know that when blood sugar isn’t balanced, it can cause fatigue, mood changes, and increased hunger.

Additionally, women who are considered lean are more prone to hypoglycemia (a.k.a. low blood sugar). This can also lead to fatigue. Other signs of hypoglycemia include muscle fatigue, nervousness, sweating, shakes, headaches, and vision changes.

2. Thyroid health

It is very important to assess the thyroid when dealing with PCOS. For one reason, hypothyroidism can look very similar to PCOS symptoms. These can include fatigue, weight gain, irregular cycles, hair loss, depression, and low libido. Additionally, research suggests that women with PCOS are at a higher risk of developing hypothyroidism. One of the explanations is that the diabetes and insulin resistance commonly seen in PCOS, can decrease Free T3 (active thyroid hormone) production. This can cause many hypothyroidism symptoms and eventually increase TSH.

Furthermore, women with PCOS seem to have higher thyroid antibody levels. Thyroid peroxidase antibodies seen in Hashimoto’s Thyroiditis have been shown to be present in women with PCOS4. Additionally, it’s theorized that women with PCOS may be more predisposed to autoimmune disease. More investigation needs to be done on this, but it gives us an idea on how we can fully assess the thyroid when it comes to PCOS.

3. Vitamin or Mineral Deficiencies

Regardless of whether PCOS is present, it’s always important to screen for blood deficiencies to assess possible fatigue causes. These tests include Vitamin B12, Vitamin D, hemoglobin and iron. Low iron levels is one of the primary causes of anemia. Additionally, since B12 is used in red blood cells production, low levels can also cause anemia. Vitamin D is very unique in its wide range of functions throughout the body. For example, one double-blind RCT study showed that Vitamin D administered to otherwise healthy individuals with fatigue, it improved their symptoms compared to the control group2. It is so important to complete a blood test for various nutrients to ensure that deficiencies aren’t present.

4. Sleep

Clinically, significant insomnia is seen more often in women with PCOS. In fact, according to the Athens Insomnia Scale (AIS) clinically significant insomnia was discovered in 12.6% of a group of 95 women with PCOS1. One of the explanations has to do with Obstructive Sleep Apnea (OSA). Women with PCOS are 2.26x more likely to develop sleep apnea3. Additionally, PCOS women showed a higher risk of developing sleep apnea in all 3 BMI categories. The greatest risk occurs with a BMI of >30 kg/m2.

One of the causes of Obstructive Sleep Apnea is insulin resistance. As we know, insulin resistance can lead to increased weight gain. Furthermore, obesity has been shown to be one of the strongest risk factors for Obstructive Sleep Apnea.


  1. Franik, G., Krysta, K., Madej, P., Gimlewicz-Pięta, B., Oślizło, B., Trukawka, J., & Olszanecka-Glinianowicz, M. (2016). Sleep disturbances in women with polycystic ovary syndrome. Gynecological Endocrinology, 32(12), 1014–1017. https://doi.org/10.1080/09513590.2016.1196177
  2. Nowak, A., Boesch, L., Andres, E., Battegay, E., Hornemann, T., Schmid, C., Krayenbuehl, P. A. (2016). Effect of vitamin D3 on self-perceived fatigue A double-blind randomized placebo-controlled trial. Medicine (United States), 95(52). https://doi.org/10.1097/MD.0000000000005353
  3. PCOS doubles risk for obstructive sleep apnea. (n.d.). Retrieved May 4, 2021, from https://www.healio.com/news/endocrinology/20190219/pcos-doubles-risk-for-obstructive-sleep-apnea
  4. Singla, R., Gupta, Y., Khemani, M., & Aggarwal, S. (2015, January 1). Thyroid disorders and polycystic ovary syndrome: An emerging relationship. Indian Journal of Endocrinology and Metabolism, Vol. 19, pp. 25–29. https://doi.org/10.4103/2230-8210.146860