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Subtle Signs Your Blood Sugar is Too High

Watch out for these tell-tale clues.
FACT CHECKED BY Emilia Paluszek

Being a board-certified Endocrinologist in New York City, I have the privilege of evaluating many patients with various glucose issues. My practice primarily focuses on general endocrinology which includes many patients with both type one and type two diabetes as well as pre-diabetes, polycystic ovarian syndrome, insulin resistance, overweight, obesity and other endocrine conditions such as thyroid disorders, osteoporosis, menopause and more. Knowing about glucose is very important to optimizing one's health given that many chronic conditions in this modern day can be linked to excess of glucose (from this point onward, the term glucose will be used interchangeably with the word "sugar") throughout the body which, in turn creates insulin resistance. Read on to find out more—and to ensure your health and the health of others, don't miss these Sure Signs You've Already Had COVID.


Why You Should Worry About High Blood Sugar

Doctor in white medical lab coat points ballpoint pen on anatomical model of human or animal pancreas

Insulin is a hormone produced by the pancreas, an important organ in the abdomen near the stomach. The pancreas produces insulin in response to glucose intake, ingested primarily in the form of carbohydrates. Fructose is another type of dietary sugar (fruits, added sugars in processed foods, sugary drinks) that is metabolized slightly differently than glucose but can also produce a slight blood glucose elevation (aka sugar spike). 

In order to regulate blood sugar levels, insulin is produced whenever carbohydrates are ingested and over time with repeated intake of these foods, repeated glucose and insulin spikes, resistance to the hormone insulin may develop. Because of this resistance, the body has to over-produce insulin. High insulin levels or hyperinsulinemia is part of the underlying cause of many chronic conditions including cardiovascular disease and those which make up metabolic syndrome: high blood pressure, high cholesterol, prediabetes and diabetes, overweight/obesity. Elevated glucose levels cause damage to tissues in the body, especially blood vessels — large and small. The small blood vessels are especially vulnerable and when negatively impacted, they can lead to eye disease, kidney disease, nerve disease, and dementia. 

Knowing what spikes one's glucose levels (and therefore insulin levels) and keeping glucose levels better controlled ultimately leads to better health. Normal blood glucose levels are less than 100 mg/dL upon waking after an overnight fast and less than 140 mg/dL 2 hours after the start of a meal. Subtle glucose spikes may not produce symptoms. People typically experience the classic symptoms of high blood sugar when their glucose levels are over 250 mg/dL but some who are sensitive may have symptoms at levels between 180-250 mg/dL. Read on to find out signs your blood sugar is too high.


You're Thirsty

Close-up of pretty young woman drinking water from glass

One sign that a person has elevated blood sugar is increased thirst which goes hand in hand with increased urination. When glucose levels increase, insulin spikes. Under normal circumstances, the insulin would effectively cause the glucose to enter cells where it's needed for fuel (muscle cells in particular). However, if glucose levels are too high and/or if a person has insulin resistance, the insulin may not be effective in transfering glucose from the blood into the body tissues. What follows is that higher than normal levels of glucose remain in the bloodstream. 

Our blood is continuously filtered by the kidneys and ideally they'd eliminate what we don't need and reabsorb what we do need back into the bloodstream. Above a certain level, the kidneys eliminate glucose in the urine. This is where knowing a bit of biochemistry is helpful – when glucose is eliminated in urine, water follows and is eliminated as well. This increased elimination of glucose and water increases urination and as a result, increases thirst. 


Your Mood Changes

Offended woman sitting back to lover looking away avoiding talking

Mood changes can also be a symptom of high blood sugar. Fluctuations in blood sugar may lead to irritability, anxiety or lethargy. While there are other potential causes of these mood changes including triggers in our environment, hormone changes, stress, mineral and vitamin deficiencies, dehydration and more, it's important to highlight the potential contribution of fluctuations in blood sugar to one's mood. 

When glucose spikes, insulin is produced and if the insulin response is robust, the rapid drop in glucose can level lead to symptoms that overlap with low blood sugar: lethargy, shakiness, headache, dizziness for example. If a person is interested in gauging whether or not mood swings are linked to glucose fluctuations, keeping a food diary may be helpful to note the time and content of food intake and the timing of any symptoms throughout the day to possibly correlate the two.


You Have Blurry Vision

Mature woman takes off her glasses and massages eyes.

Blurry vision is also a sign of high blood sugar. The lens of the eye is sensitive to the blood glucose concentration and fluctuations in blood glucose or even sustained high blood glucose may change the shape of the lens. When the lens is swollen or changes shape, the eye has more difficulty focusing and vision blurs. Often, people think they need new glasses but once their blood glucose levels stabilize, which can take a few months, their vision stabilizes as well. 

Other possible causes of blurry vision are cataracts (they cause the lens to become cloudy) and glaucoma (increased pressure in the eye because of poor drainage). These conditions do occur more frequently in patients with high blood glucose/diabetes. 


You Feel Hunger and Sugar Cravings

woman eating bite of chocolate bar

People with high blood glucose are likely to experience hunger and sugar cravings. This can occur despite regular food intake and snacking and is not necessarily related to stress or emotional eating. In the setting of high blood glucose levels, especially if levels are high in a sustained manner, a person may develop insulin resistance. Insulin is critical in glucose regulation and when the body tissues do not respond to insulin well (insulin resistance), the glucose is not able to effectively enter cells and the body perceives that glucose is not available. 

The body responds to this by creating signals which activate hunger centers in the brain and increase appetite (hyperphagia). If a person with high blood sugar feels increased hunger they may eat food and again because the glucose doesn't enter cells, the hunger signals continue.


You Experience Unexplained Weight Loss

weight loss

The insulin resistance that may accompany high blood sugar creates an environment in the body whereby the cells do not perceive they are receiving fuel. This is because glucose is not able to enter the cells as effectively as they would if insulin was working well. Due to this perceived lack of energy, the body burns other fuels and as a result the body enters a state of catabolism (breakdown) and weight loss ensues. 


You Experience Some of These Symptoms

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Other signs of high blood glucose include fatigue, increased frequency of infections and poor wound healing. High sugar levels can lead to low energy states, again because the body perceives it is under-fueled despite having plenty of glucose. High glucose levels compromise the immune system which can contribute to a higher frequency of infections in those with chronically elevated sugar levels. 

The most common infections are yeast infections or other fungal infections as well as urinary tract infections. Partly due to a compromised immune system and partly due to the toxic effects of excess glucose on our body tissues, we also see poor wound healing, such as a skin ulcer that isn't healing, in those with chronically elevated levels. 


What You Should Do if You Notice These Signs?

Doctor with glucometer and insulin pen device talking to male patient at medical office in hospital.

If someone notices signs of high blood sugar, the first thing to do is to discuss your concerns with your physician and to work with them to get to the root cause of the symptoms. Many of these symptoms overlap with other issues such as vitamin or mineral deficiencies, thyroid dysfunction, a poor diet, dehydration, poor sleep, chronic stress and more. 

One should examine their lifestyle and identify areas which need optimization and consider keeping a diary of habits and their symptoms to be better able to detect possible correlations. If there is room for dietary improvement to reduce or eliminate the intake of refined and processed foods and obvious sources of sugar that is a key step in the road to better health.

Minisha Sood, MD, FACE, ECNU, is an Assistant Professor at the Hofstra School of Medicine and a board-certified Endocrinologist/Obesity Medicine specialist at Lenox Hill Hospital.

Minisha Sood, MD, FACE, ECNU
Assistant Professor Hofstra School of Medicine, Division of Endocrinology, Diabetes & Metabolism New York, NY Read more about Minisha