Thyroid and Blood Sugar Relationship

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In order to function properly, your body needs energy.

Blood sugar, also known as blood glucose, is the primary source of fuel for energy production, particularly for your muscles, brain, and other parts of the body.

In addition, blood sugar is a building block for bigger molecule structures and plays a major role in your health and wellbeing.

Changes in blood sugar levels affect the metabolic processes and affect the entire body.

Since thyroid problems are common as well as problems with blood sugar, it is impossible not to wonder if they could be connected to some people.

You’ll find more info about this important subject below.

Thyroid and high blood sugar

High blood sugar, or hyperglycemia, is a common health concern affecting millions of people. There are two main types of hyperglycemia[i]:

  • Fasting hyperglycemia – blood sugar levels higher than 130 mg/dl (milligrams per deciliter) and it usually occurs when a person doesn’t eat or drink for more than eight hours
  • Postprandial (after-meal) hyperglycemia – blood sugar levels higher than 180 mg/dl about two hours after the meal. That being said, nondiabetic individuals rarely have blood sugar levels higher than 140 mg/dl after they eat

The relationship between high blood sugar and thyroid functioning can be discussed from different angles including insulin resistance, metabolic syndrome, and diabetes.

Insulin resistance

Insulin is a hormone produced by the pancreas and its purpose is to allow cells in the body to use blood sugar for energy. In people with insulin resistance, cells don’t use insulin efficiently.

As a result, it becomes difficult for those cells to absorb glucose, thus creating a buildup of blood sugar in the blood.

Evidence shows that in most cases, insulin resistance manifests at the cellular level through post-receptor defects in insulin signaling[ii].

It is estimated that 60-70 million people in the US have insulin resistance.

In addition, about 40% of individuals who are 50 or older are at a higher risk[iii] of developing this health problem. Insulin resistance may be a part of metabolic syndrome and it precedes the development of type 2 diabetes.

Studies show that insulin resistance is strongly related to thyroid disorders.

Although the relationship between thyroid hormone levels and insulin is complicated, it does play a role in the pathogenesis of insulin resistance. In fact, insulin levels are higher in patients with hypothyroidism as well as individuals who deal with hyperthyroidism.

Thyroid disorders are linked to insulin resistance, and thereby high blood sugar levels, due to multiple mechanisms like altered lipid levels and insulin secretion.

More research is necessary on this topic, but a growing body of evidence confirms that altered thyroid state could lead to insulin resistance and blood glucose-related disorder called diabetes dyslipidemia[iv] (abnormal amount of lipids in the blood).

The International Journal of Health Sciences and Research published results of the study which confirmed that thyroid dysfunction alters lipid and glucose metabolism, which is a major risk factor for cardiovascular diseases.

Scientists also discovered that hypothyroidism is strongly associated with higher insulin levels and insulin resistance and correlates negatively with T3 and T4 hormones and positively with TSH.

These findings show that individuals with hypothyroidism are at a higher risk of developing insulin resistance[v] (through altered glucose and fat metabolism) and health problems associated with it.

Metabolic syndrome

As shown above, insulin resistance plays a role not only in type 2 diabetes but in metabolic syndrome as well.

Now that we have established a connection between insulin resistance and impaired blood sugar metabolism with thyroid disorders, let’s take a closer look at metabolic syndrome.

Metabolic syndrome is a combination of different conditions including:

  • High blood pressure
  • High blood sugar
  • Excess body fat around waist
  • Abnormal cholesterol and triglyceride levels

These conditions occur together and increase the risk of diabetes, stroke, or heart disease. This health problem is strongly related to sedentary lifestyle and overweight or obesity. Insulin resistance is considered one of the major causes of metabolic syndrome.

Figures show that nearly 35% of all adults in the US and 50% of those who are 60 or older had metabolic syndrome in 2011-2012[vi].

A growing body of evidence confirms the link between metabolic syndrome and thyroid disorders, both hyper- and hypothyroidism. Numerous factors determine blood glucose levels, such as:

  • A balance gluconeogenesis (biosynthesis of new glucose) and glucose ingestion
  • Glucose metabolism and disposal in target tissues

Hypothyroidism is related to decreased transport of blood sugar in myocytes (muscle cells). This is regulated by glucose transporters located on the surface of cell which controls the glucose uptake on intracellular level.

Thyroid hormone stimulates basal expressions of glucose transporters. In hyperthyroidism, glucose transporters expression is increased.

Therefore, thyroid hormones have an important effect on insulin clearance and secretion, which could describe why thyroid disorders are linked with insulin resistance[vii].

One study enrolled 169 metabolic syndrome patients and discovered that 31.9% of them had thyroid dysfunction too. Most participants, about 26.6%, had subclinical hypothyroidism while overt hypothyroidism was recorded in 3.5% individuals.

About 1.7% people who took part in this study had hyperthyroidism. Thyroid dysfunction was more common among female patients with metabolic syndrome. In addition, there were significant differences in waist circumference and cholesterol levels among metabolic syndrome patients with and without thyroid dysfunction.

Those with thyroid problems had bigger waist circumference and lower levels of HDL or good cholesterol[viii].

Type 2 diabetes

Type 2 diabetes is the most common form of diabetes, a health problem wherein blood sugar levels increase to higher levels than it is normal.

According to the CDC, more than 29 million Americans have diabetes, which is about 9.3% of the entire population. In other words, 1 out of every 11 people in the US has diabetes while 1 out of 4 people doesn’t even know they have it.

It is estimated that 1 in 3 people will develop type 2 diabetes at some point in their life[ix].

The journal BMC Medicine published results of an interesting study which found that higher levels of thyroid stimulating hormone (TSH) and lower levels of T4 are linked with an increased risk of diabetes and progression from prediabetes to diabetes (by the way, see our common thyroid questions and answers if you’re not sure what these hormones are or what they do.)

In fact, that is the very first study to describe the relationship between thyroid function within normal range and risk of diabetes.

Several mechanisms could explain the relationship between low and low-normal thyroid function and diabetes risk, including:

  • Decreased insulin sensitivity
  • Tolerance of blood sugar due to reduced ability of insulin to enhance utilization of glucose in muscle primarily
  • Downregulation of plasma membrane glucose transporters

Interestingly, even though hyperthyroidism is also linked with incidence of insulin resistance, high and high-normal thyroid function exhibit protective effects against the development and progression to diabetes, evidence shows.

Why does this happen?

One theory is that insulin resistance in patients with hyperthyroidism is counterbalanced by some other mechanisms related to the prolonged excess of thyroid hormone[x].

One study analyzed the prevalence of thyroid disorders among 202 patients with type 2 diabetes.

Scientists discovered that 33 participants or 16.3% of them had subclinical hypothyroidism, 23 individuals or 11.4% had hypothyroidism while 4 people had subclinical hyperthyroidism and 3 patients had hyperthyroidism.

Results indicate that prevalence of hypothyroidism is high among patients with type 2 diabetes, particularly among those who are older than 45 and their BMI is bigger than 25[xi].

Thyroid and low blood sugar

When the term blood sugar comes to mind, we usually think of high blood glucose levels, insulin resistance, and other problems.

While these issues are common and pose a major threat to our wellbeing, it is also important to bear in mind low blood sugar isn’t good for your health either.

Hypoglycemia, or low blood sugar, is a potentially dangerous condition indicated by insufficient glucose amounts for production of energy in the body’s cells.

Main causes of low blood sugar are certain medications, tumors, endocrine disorders, and some medical conditions.

Studies reveal that hypothyroidism is associated with different hormonal, biochemical, and nervous system abnormalities which have the potential to contribute to hypoglycemia.

For example, hypothyroidism is related to low growth hormone and cortisol responses to insulin-induced hypoglycemia, thus blocking the proper counter regulatory protection.

When blood sugar levels decrease, the adrenal glands address this issue by secreting hormone cortisol. Then, the hormone sends a signal which tells the liver to produce higher amounts of blood sugar, thus bringing the levels of glucose to normal.

The problem occurs when the repeated release of cortisol in patients with hypoglycemia suppresses pituitary function. The thyroid gland can’t operate properly without adequate pituitary functioning.

Evidence suggests that dysfunction of pituitary could be a direct consequence of hypothyroidism, rather than a cause of thyroid dysfunction.

Bearing in mind that the roles of gluconeogenesis in adipose tissue and skeletal muscle and glycogenolysis (breakdown of glycogen) are impaired in hypothyroid patients, they lead to delayed hypoglycemia recovery[xii].

Maintaining healthy blood sugar levels

Both high and low blood sugar levels are potentially harmful to your health, which is why it is mandatory to keep them within a healthy range.

This is particularly important if you have hypothyroidism, thyroid disorder associated with weight gain, high cholesterol, and other symptoms affecting your heart health.

Below, you’ll find useful tips that will help you maintain healthy blood sugar levels:

  • Consume an anti-inflammatory diet rich in protein, fiber, and healthy fats that stabilize blood sugar levels, especially when consuming carbs
  • Exercise regularly because physical activity helps manage blood sugar levels by encouraging muscles that take up more glucose and making cells more responsive to insulin, in order to prevent insulin resistance
  • Manage stress; this goes without even saying. As seen above, stress hormone cortisol can interfere with production of thyroid hormones and contribute to hypothyroidism
  • Don’t skip meals, particularly breakfast. Skipping meals could increase the levels of blood sugar, which isn’t the effect you want to achieve. Plus, the habit to skip meals can also make you gain weight, rather than losing it
  • Get enough sleep in order to boost energy levels, improve productivity, and be more active. Plus, sleep is a great way to combat or prevent stress and reduce the levels of cortisol. Ideally, you should set a precise sleep pattern and go to bed every night at the same time and wake up every morning at the same time as well. Try this for a month and you’ll notice changes in your behavior, productivity, and energy levels


Blood sugar serves as fuel for energy production in the cells, and it is of huge importance to our overall health and wellbeing. Thyroid function is closely related to both high and low blood sugar levels.

Although keeping blood sugar levels at a healthy range isn’t the easiest job in the world, it is mandatory in order to prevent unfortunate scenarios.

This post elucidated the relationship between low and high blood sugar levels in individuals with thyroid problems. Keep your blood sugar levels in check with tips and tricks mentioned above.


[i] High blood sugar and diabetes, WebMD

[ii] Wilcox G. Insulin and Insulin Resistance. Clinical Biochemist Reviews. 2005;26(2):19-39.

[iii] Insulin resistance: recognizing the hidden danger, Pharmacy Times

[iv] Kapadia KB, Bhatt PA, Shah JS. Association between altered thyroid state and insulin resistance. Journal of Pharmacology & Pharmacotherapeutics. 2012;3(2):156-160. doi:10.4103/0976-500X.95517.

[v] Vyakaranam S, Vanaparthy S, Nori S, Palarapu S, Bhongir AV. Study of Insulin Resistance in Subclinical Hypothyroidism. International journal of health sciences and research. 2014;4(9):147-153.

[vi] Aguilar M, Bhuket T, Torres S, et al. Prevalence of the metabolic syndrome in the United States, 2003-2012. JAMA May 2015;313(19):1973-1974. Doi: 10.1001/jama.2015.4260

[vii] Iwen KA, Schröder E, Brabant G. Thyroid Hormones and the Metabolic Syndrome. European Thyroid Journal. 2013;2(2):83-92. doi:10.1159/000351249.

[viii] Khatiwada S, Sah SK, Rajendra KC, et al. Thyroid dysfunction in metabolic syndrome patients and its relationship with components of metabolic syndrome. Clinical Diabetes and Endocrinology February 2016. Doi: 10.1186/s40842-016-0021-0

[ix] Diabetes latest, CDC

[x] Chaker L, Ligthart S, Korevaar TIM, et al. Thyroid function and risk of type 2 diabetes: a population-based prospective cohort study. BMC Medicine. 2016;14:150. doi:10.1186/s12916-016-0693-4.

[xi] Demitrost L, Ranabir S. Thyroid dysfunction in type 2 diabetes mellitus: A retrospective study. Indian Journal of Endocrinology and Metabolism. 2012;16(Suppl 2):S334-S335. doi:10.4103/2230-8210.104080.

[xii] Kalra S, Unnikrishnan AG, Sahay R. The hypoglycemic side of hypothyroidism. Indian Journal of Endocrinology and Metabolism. 2014;18(1):1-3. doi:10.4103/2230-8210.126517.

1 Comment
  1. Reply
    Sandta June 27, 2018 at 3:39 pm

    Does donating blood once a month affect blood sugar levels/thyroid???

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