People with full-blown type 2 diabetes are not able to use the hormone insulin properly, and have what’s called insulin resistance. Insulin is necessary for glucose, or sugar, to get from your blood into your cells to be used for energy. When there is not enough insulin — or when the hormone doesn’t function as it should — glucose accumulates in the blood instead of being used by the cells. This sugar accumulation may lead to the aforementioned complications.
In people with type 1 diabetes, the symptoms often begin abruptly and dramatically. A serious condition called diabetic ketoacidosis, a complication in which the body produces excess acid, may quickly develop. In addition to the usual diabetes symptoms of excessive thirst and urination, the initial symptoms of diabetic ketoacidosis also include nausea, vomiting, fatigue, and—particularly in children—abdominal pain. Breathing tends to become deep and rapid as the body attempts to correct the blood’s acidity (see Acidosis), and the breath smells fruity and like nail polish remover. Without treatment, diabetic ketoacidosis can progress to coma and death, sometimes very quickly.
Some risks of the keto diet include low blood sugar, negative medication interactions, and nutrient deficiencies. (People who should avoid the keto diet include those with kidney damage or disease, women who are pregnant or breast-feeding, and those with or at a heightened risk for heart disease due to high blood pressure, high cholesterol, or family history. (40)
^ Jump up to: a b c d Inzucchi, SE; Bergenstal, RM; Buse, JB; Diamant, M; Ferrannini, E; Nauck, M; Peters, AL; Tsapas, A; Wender, R; Matthews, DR (March 2015). "Management of hyperglycaemia in type 2 diabetes, 2015: a patient-centred approach. Update to a Position Statement of the American Diabetes Association and the European Association for the Study of Diabetes". Diabetologia. 58 (3): 429–42. doi:10.1007/s00125-014-3460-0. PMID 25583541.
Poor vision, limited manual dexterity due to arthritis, tremor, or stroke, or other physical limitations may make monitoring blood glucose levels more difficult for older people. However, special monitors are available. Some have large numerical displays that are easier to read. Some provide audible instructions and results. Some monitors read blood glucose levels through the skin and do not require a blood sample. People can consult a diabetes educator to determine which meter is most appropriate.
The primary complications of diabetes due to damage in small blood vessels include damage to the eyes, kidneys, and nerves.[32] Damage to the eyes, known as diabetic retinopathy, is caused by damage to the blood vessels in the retina of the eye, and can result in gradual vision loss and eventual blindness.[32] Diabetes also increases the risk of having glaucoma, cataracts, and other eye problems. It is recommended that diabetics visit an eye doctor once a year.[33] Damage to the kidneys, known as diabetic nephropathy, can lead to tissue scarring, urine protein loss, and eventually chronic kidney disease, sometimes requiring dialysis or kidney transplantation.[32] Damage to the nerves of the body, known as diabetic neuropathy, is the most common complication of diabetes.[32] The symptoms can include numbness, tingling, pain, and altered pain sensation, which can lead to damage to the skin. Diabetes-related foot problems (such as diabetic foot ulcers) may occur, and can be difficult to treat, occasionally requiring amputation. Additionally, proximal diabetic neuropathy causes painful muscle atrophy and weakness.
^ Jump up to: a b Funnell, Martha M.; Anderson, Robert M. (2008). "Influencing self-management: from compliance to collaboration". In Feinglos, Mark N.; Bethel, M. Angelyn. Type 2 diabetes mellitus: an evidence-based approach to practical management. Contemporary endocrinology. Totowa, NJ: Humana Press. p. 462. ISBN 978-1-58829-794-5. OCLC 261324723.

One particular type of sugar that has attracted a lot of negative attention is high-fructose corn syrup (HFCS) — and for good reason, as multiple studies suggest HFCS can influence diabetes risk. Some research in people who are overweight and obese, for example, suggests regularly consuming drinks sweetened with either fructose, a byproduct of HFCS, or glucose can lead to weight gain, and drinks with fructose in particular may reduce insulin sensitivity and spike blood sugar levels.

Jump up ^ Haw, JS; Galaviz, KI; Straus, AN; Kowalski, AJ; Magee, MJ; Weber, MB; Wei, J; Narayan, KMV; Ali, MK (6 November 2017). "Long-term Sustainability of Diabetes Prevention Approaches: A Systematic Review and Meta-analysis of Randomized Clinical Trials". JAMA Internal Medicine. 177 (12): 1808–17. doi:10.1001/jamainternmed.2017.6040. PMID 29114778.
Type 2 diabetes mellitus (non–insulin-dependent diabetes mellitus [NIDDM]) is a heterogeneous disorder. Most patients with type 2 diabetes mellitus have insulin resistance, and their beta cells lack the ability to overcome this resistance. [6] Although this form of diabetes was previously uncommon in children, in some countries, 20% or more of new patients with diabetes in childhood and adolescence have type 2 diabetes mellitus, a change associated with increased rates of obesity. Other patients may have inherited disorders of insulin release, leading to maturity onset diabetes of the young (MODY) or congenital diabetes. [7, 8, 9] This topic addresses only type 1 diabetes mellitus. (See Etiology and Epidemiology.)

Diabetes mellitus, or as it's more commonly known diabetes, is a disease characterized by an excess of blood glucose, or blood sugar, which builds up in the bloodstream when your body isn't able to adequately process the sugar in food. High blood sugar is an abnormal state for the body and creates specific symptoms and possible long-term health problems if blood sugar is not managed well.
Fasting plasma glucose level: If your blood glucose level is 7.0 mmol/L or higher after having not eaten anything for at least 8 hours – called fasting – your doctor may diagnose diabetes. If your blood glucose level is between 6.1 to 6.9 mmol/L, your doctor may diagnose impaired fasting glucose or prediabetes (a condition that may later develop into diabetes).
While unintentional weight loss may seem like a dream to some people, it can also be a scary sign that your pancreas isn’t working the way it’s supposed to. Accidental weight loss is often one of the first signs of diabetes. However, weight loss may also help you prevent developing the condition in the first place. In fact, losing just 5 percent of your body weight may lower your risk of diabetes by as much as 58 percent. And when you’re ready to ditch a few pounds, start by adding the 40 Healthy Snack Ideas to Keep You Slim to your routine.
People with T2D produce insulin, but their bodies don’t use it correctly; this is referred to as being insulin resistant. People with type 2 diabetes may also be unable to produce enough insulin to handle the glucose in their body. In these instances, insulin is needed to allow the glucose to travel from the bloodstream into our cells, where it’s used to create energy.
Many studies have shown that awareness about the diabetes and its complications is poor among the general population specially in the rural areas6,7. There is an urgent need to create awareness among the population regarding diabetes and about the serious consequences of this chronic disorder. Epidemiological data from India have shown the presence of a number of risk factors which can be easily identified by simple non-invasive risk scores8,9. The major risk factors are listed in Box 1.
Diabetes has often been referred to as a "silent disease" for two reasons: 1) Many people with Type 2 diabetes walk around with symptoms for many years, but are not diagnosed until they develop a complication of the disease, such as blindness, kidney disease, or heart disease; 2) There are no specific physical manifestations in individuals with diabetes.  Therefore, unless a person chooses to disclose their disease, it is possible that friends and even family members may be unaware of a person's diagnosis.
Periodontal Disease. Periodontal disease is a commonly observed dental problem for patients with diabetes. It is similar to the periodontal disease encountered among nondiabetic patients. However, as a consequence of the impaired immunity and healing associated with diabetes, it may be more severe and progress more rapidly (see Right). The potential for these changes points to the need for periodic professional evaluation and treatment.
What is hypoglycemia? A blood sugar level of under 70 mg/dl (3.9 mmol/l) is typically considered hypoglycemia (low blood sugar), and can result in irritability, confusion, seizures, and even unconsciousness for extreme lows. To correct hypoglycemia, patients commonly use fast-acting carbohydrates. In extreme cases of severe hypoglycemia, a glucagon injection pen can be used. According to the Mayo Clinic, symptoms of hypoglycemia are:

The American Diabetes Association recommends that blood sugars be 80mg/dL-130mg/dL before meals and less than or equal to 180mg/dL two hours after meals. Blood sugar targets are individualized based on a variety of factors such as age, length of diagnosis, if you have other health issues, etc. For example, if you are an elderly person, your targets maybe a bit higher than someone else. Ask your physician what targets are right for you.
Another area of pathologic changes associated with diabetes mellitus is the nervous system (diabetic neuropathy), particularly in the peripheral nerves of the lower extremities. The patient typically experiences a “stocking-type” anesthesia beginning about 10 years after the onset of the disease. There may eventually be almost total anesthesia of the affected part with the potential for serious injury to the part without the patient being aware of it. In contrast, some patients experience debilitating pain and hyperesthesia, with loss of deep tendon reflexes.
Home blood sugar (glucose) testing is an important part of controlling blood sugar. One important goal of diabetes treatment is to keep the blood glucose levels near the normal range of 70 to 120 mg/dl before meals and under 140 mg/dl at two hours after eating. Blood glucose levels are usually tested before and after meals, and at bedtime. The blood sugar level is typically determined by pricking a fingertip with a lancing device and applying the blood to a glucose meter, which reads the value. There are many meters on the market, for example, Accu-Check Advantage, One Touch Ultra, Sure Step and Freestyle. Each meter has its own advantages and disadvantages (some use less blood, some have a larger digital readout, some take a shorter time to give you results, etc.). The test results are then used to help patients make adjustments in medications, diets, and physical activities.
A1C: Your A1C, also called glycated hemoglobin, reflects your average blood glucose levels for the past 2 to 3 months. If your A1C is 6.5% or greater, your doctor may diagnose diabetes. If your A1C is between 6.0% and 6.4%, your doctor may diagnose prediabetes. Of note, A1C cannot be used to diagnose type 1 diabetes, diabetes in children, adolescents, or pregnant women.
DKA usually follows increasing hyperglycemia and symptoms of osmotic diuresis. Users of insulin pumps, by virtue of absent reservoirs of subcutaneous insulin, may present with ketosis and more normal blood glucose levels. They are more likely to present with nausea, vomiting, and abdominal pain, symptoms similar to food poisoning. DKA may manifest as respiratory distress.

Type 2 DM is characterized by insulin resistance, which may be combined with relatively reduced insulin secretion.[11] The defective responsiveness of body tissues to insulin is believed to involve the insulin receptor. However, the specific defects are not known. Diabetes mellitus cases due to a known defect are classified separately. Type 2 DM is the most common type of diabetes mellitus.[2]

Type 1 diabetes occurs when your immune system, the body’s system for fighting infection, attacks and destroys the insulin-producing beta cells of the pancreas. Scientists think type 1 diabetes is caused by genes and environmental factors, such as viruses, that might trigger the disease. Studies such as TrialNet are working to pinpoint causes of type 1 diabetes and possible ways to prevent or slow the disease.

Insulin treatment can cause weight gain and low blood sugar. In addition, there may be discomfort at the injection site. There are several types of tablets used to treat diabetes and they have different side-effects. The most common are diarrhoea (metformin), nausea (GLP-1 agoniists), weight-gain (sulphonylureas and pioglitazone), low blood sugar (sulphonylureas) and genital thrush (SGLT2 inhibitors). However, not all patients will experience some or any of these side-effects and patients should discuss any concerns with their doctor.

In this health topic, we explain the dangers of hyperglycemia, or high blood sugar levels, and diabetes. Hyperglycemia causes many of the warning signs of diabetes listed above. Hyperglycemia may be caused by skipping or forgetting your insulin or diabetes medicine, eating too many grams of carbs for the amount of insulin administered, simply eating too many grams of carbs in general, or from stress or infections.