10 symptoms of diabetes [early warning signs]

What is diabetes mellitus?

Diabetes mellitus (DM) is the disease caused by too much glucose, a type of sugar, in the bloodstream. There are basically two types of diabetes:

Type 1 diabetes mellitus (DM1): a chronic disease that occurs when the pancreas produces little or no insulin, a hormone that helps the body absorb and utilize sugar from food. Without insulin, blood glucose levels become higher than normal, a condition called hyperglycemia.

Type 2 diabetes mellitus (DM2): a chronic disease that occurs through a combination of insufficient insulin production and the body’s resistance to it. To explain further, the patient’s pancreas produces insulin, but the amount is not ideal, and it still malfunctions. DM2 is closely linked to a sedentary lifestyle and being overweight.

In DM2, the first signs and symptoms can be mild and go unnoticed. Some people may have the disease almost silently for several years, only to discover it accidentally through blood tests requested for some other reason.

Those who are never tested may discover the disease much later, when there are already serious symptoms caused by damage to organs such as the eyes, kidneys, nerves, heart, or skin.

DM1, on the other hand, usually has more severe and easily recognized early symptoms, which is why the disease is usually identified early, before there is organ damage.

In this article we will only discuss the early symptoms of diabetes, those that serve as a warning about the possibility of the disease. Here we will not discuss target organ damage caused by long-term hyperglycemia.

Nor will we talk about pre-diabetes, which is a phase in which blood glucose levels are above normal, but not yet high enough to characterize diabetes mellitus (read: Pre-Diabetes – Diagnosis, Risks, and Treatment).

Signs and symptoms of early-stage diabetes

The 10 most common early signs and symptoms of diabetes are:

  • Polyuria (urinating all the time).
  • Polydipsia (excessive sensation of thirst).
  • Tiredness and lack of energy.
  • Weight loss.
  • Polyphagia or hyperphagia (frequent hunger).
  • Blurry vision.
  • Slow healing.
  • Frequent infections.
  • Bad breath.
  • Diabetic ketoacidosis.

excess urine

Excess urine, called polyuria in medicine, is one of the first signs of diabetes.

Under normal conditions, there is no glucose in the urine, as all the glucose that reaches the kidney tubules is reabsorbed back into the blood. However, when there is hyperglycemia, usually with values ​​above 180 mg/dl, the amount of sugar that reaches the kidneys is so large that it is not able to reabsorb everything, allowing the loss of glucose in the urine.

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Since we cannot urinate pure sugar, the kidney needs to dilute the glucose in order to get rid of it. Therefore, the higher the blood glucose (concentration of glucose in the blood), the more intense the glycosuria (loss of glucose in the urine) and the greater the volume of urine produced throughout the day.

Excessive thirst

As we have seen, the diabetic patient urinates excessively. As a result, they lose more water than they are supposed to and become dehydrated. Since thirst is the body’s main defense mechanism against dehydration, it comes as no surprise that diabetics need to drink more water than usual (read also: How many liters of water should we drink a day?).

The diabetic patient who does not adequately control his blood glucose, either because of poor adherence to treatment or simply because he has not yet discovered that he has diabetes, ends up in a vicious circle. The excess of glucose increases the amount of water lost in the urine, making the patient urinate very frequently. The water loss causes dehydration, which in turn triggers excessive thirst. The patient drinks a lot of water, but because the glucose is still too high in the blood, he keeps urinating all the time.


Chronic fatigue is another common symptom of diabetes and occurs due to two factors:

a. By dehydration, whose mechanism was explained in the previous topic.
b. The inability of the cells to receive glucose.

Glucose is the cells’ main source of energy; it is our body’s fuel. It is insulin that promotes the entry of glucose from the blood into the cells, which in type 1 diabetes is non-existent, and in type 2 diabetes does not work well.

Therefore, as the cells receive less glucose than necessary, the body as a whole produces less energy, which leads to symptoms such as fatigue and feelings of lack of energy.

Weight Loss

Weight loss is a very common symptom in type 1 diabetes. It can also occur in type 2 diabetes, but is not as frequent.

Insulin is also the hormone responsible for fat storage and protein synthesis in the body. Since there is an absence of insulin in type 1 diabetes, the patient stops storing fat and stops producing muscle. Furthermore, since there is no glucose to generate energy, the cells end up having to generate it from the breakdown of protein and fat stores in the body. In short, the body without insulin doesn’t generate muscle or fat, and still has to consume the existing reserves.

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Since in type 2 diabetes there is insulin circulating in the blood, these effects are less evident. Furthermore, in type 2 diabetes, resistance to insulin slowly and progressively becomes established over a period of years as the patient gets fatter and older. Type 1 diabetes, on the other hand, is not related to being overweight; it is a disease of immunological origin in which the production of insulin ceases relatively abruptly.

In general, the DM1 patient is thin, and the DM2 patient is overweight or obese.

Excessive hunger

Because the cells cannot get enough glucose to generate energy, the body interprets the situation as if the patient were fasting. The body needs energy, and the only way it knows how to get it is through food.

One of the characteristics of weight loss in type 1 diabetes is that it occurs despite the fact that the patient eats frequently. The patient eats, but the glucose ingested is not utilized and ends up being eliminated through urine. Because the cells receive less glucose than they need, the patient quickly feels the need to eat again. In more advanced stages of the disease, this cycle is usually interrupted, and the patient starts to lose his or her appetite, which contributes even more to the weight loss.

The type 2 diabetic patient, on the other hand, does not usually lose weight because he or she produces insulin. This insulin has difficulty getting the glucose into the cell, but it can still transform the excess glucose in the blood into fat reserves. The patient eats, a small amount goes into the cells, some comes out in the urine, and the rest is converted into fat.

Blurred vision

A very common symptom of diabetes is blurred vision. Excess glucose in the blood causes the lens of the eye to swell, changing its shape and flexibility, decreasing its ability to focus, and blurring the vision. Vision is often blurred when blood glucose is too high, and returns to normal once the diabetes is under control.

This change in the eyes has nothing to do with diabetic retinopathy, the eye complication that can arise after years of diabetes.

Poor Healing

Excess glucose in the blood, when it runs chronically, causes numerous disturbances in the functioning of the body. The difficulty in healing wounds occurs due to a decrease in the function of the cells responsible for tissue repair, decreased cell proliferation, and difficulty in generating new blood vessels.

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Over time, diabetes also causes nerve damage, causing the patient to have less sensitivity in the skin, especially in the lower limbs. Foot lesions can appear and worsen without the patient feeling much pain or discomfort. Small wounds can take time to close or even worsen over time if the patient is not careful with them.


Diabetes also causes disturbances in the immune system by altering the functioning of the defense cells. The diabetic can be considered an immunosuppressed patient and is at greater risk of developing infections, including urinary tract infection, skin infections, candidiasis, and pneumonia.

Bad Breath

Because there is a deficiency of insulin, the cells do not receive the proper amount of glucose and must use the body’s fat stores as a source of energy. The breakdown of fats generates three substances known as ketones or ketone bodies: β-hydroxybutyrate, acetoacetate, and acetone.

The ketones are eliminated in the urine and from the lungs through breathing, which is why the patient may develop a bad breath, with a somewhat sweet and sour odor. This is called ketonic breath, and can also occur in healthy people who fast for a long time or who have a very restricted carbohydrate diet.

Bad breath in diabetic patients can also be caused by gum or tooth infections, which are more common in diabetics than in the general population.

If you want to know other causes of halitosis, read: Bad Breath – Causes and Treatment.

Diabetic ketoacidosis

Diabetic ketoacidosis is a complication of type 1 diabetes, and it is often the first sign of the disease.

As explained in the previous topic, the lack of glucose in the cells leads to the production of ketone bodies. Beta-hydroxybutyrate and acetoacetate are acidic substances, which, when generated in large quantities, can cause acidification of the blood, a condition called ketoacidosis.

In situations of prolonged fasting, restrictive diets, or even in DM2, the amount of ketoacids produced is not large enough to cause severe acidosis. In DM1, however, since there is a complete absence of insulin, the production of ketoacids is immense, and the acidosis generated can be quite severe, causing the blood pH to drop to dangerous, potentially fatal levels.

Diabetic ketoacidosis is a medical emergency and usually occurs when blood glucose levels exceed 500 mg/dl.

The most common signs and symptoms of ketoacidosis are nausea, vomiting, abdominal pain, mental confusion, prostration, and difficulty breathing.