Diabetes Insipidus Vs. Diabetes Mellitus

Diabetes mellitus is characterized by high levels of sugar in the blood while diabetes insipidus is a disease where kidneys are unable to conserve water. Diabetes insipidus (DI) is a rare disease while diabetes mellitus is very common; "diabetes" in general usage refers to diabetes mellitus, which is of 3 types — gestational, Type 1 and Type 2 diabetes.

The causes, symptoms, treatment and prognosis for diabetes insipidus are different from diabetes mellitus.

Causes and Types of Diabetes

Diabetes insipidus

Diabetes insipidus, or DI, is characterized by the inability of kidneys to conserve water when they purify blood. This can be either because of:

  1. a deficiency of ADH (antidiuretic hormone or vasopressin), or
  2. a failure of the kidneys to respond to ADH

In the first case, the condition is called central DI, and in the second case it is called nephrogenic DI. Central DI is the more common form of the disease.

Central DI can be inherited or caused due to damage to either the hypothalamus (the part of the brain that produces ADH) or the pituitary gland, where ADH is stored. Head injuries, tumors, infections or surgery can inflict such damage.

Nephrogenic DI can be inherited (from mother to son) or be caused by kidney disease, hypercalcemia (excess calcium in the body) or by certain drugs such as lithium, amphotericin B, and demeclocycline.

Diabetes mellitus

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Diabetes mellitus is also closely related to a hormone — insulin. It is caused by either a deficiency of insulin or a resistance to insulin, or both. Several populations - such as Indians and African Americans - have a higher genetic predisposition to diabetes. This is compounded by lifestyle, lack of exercise, obesity and diet.

There are three types of diabetes mellitus:

  1. Type 1 Diabetes can occur at any age but is most common in children and young adults. It is characterized by insulin deficiency in the body.
  2. Type 2 Diabetes is the most common form of diabetes in the world. It is characterized by
  3. Gestational diabetes is high blood sugar that develops at any time during pregnancy in a woman who does not have diabetes.

Symptoms of diabetes

Diabetes insipidus is characterized by extreme thirst (especially for cold water or ice) and excessive urination. However, the urine does not contain glucose. Very occasionally, people with diabetes insipidus will experience blurred vision. In children, diabetes insipidus can interfere with appetite, eating, weight gain and growth.

Diabetes mellitus is characterized by high blood sugar, which also leads to excessive urination and increased thirst and hunger. Blurred vision is also a common symptom. Patients with type 2 diabetes develop symptoms slowly, so they may go undiagnosed for a long time. In contrast, type 1 diabetes patients get very sick quickly and are diagnosed immediately.


Diabetes insipidus is diagnosed by testing blood glucose levels, bicarbonate levels and calcium levels. High sodium levels in blood electrolytes can also indicate diabetes insipidus.

Diabetes mellitus is diagnosed when an individual has a fasting plasma glucose level of over 7.0 mmol/l, plasma glucose of over 11.1 mmol/l two hours after a 75g oral glucose intake, or glycated hemoglobin of more than 6.5%. Positive results must be retested on a different day.


Central diabetes insipidus and gestational diabetes insipidus can be treated with desmopressin. The anticonvulsive medication carbamazepine is also somewhat successful in treating these types of diabetes insipidus. Nephrogenic diabetes insipidus can be improved with the diuretic hydrocholorothiazide or indomethacin.

Diabetes mellitus cannot be cured. It is managed by keeping blood glucose levels as close to normal as possible. Type 1 diabetes can be treated with insulin injections or an insulin pump. Type 2 diabetes is treated through exercise, careful diet, and occasionally by insulin in a long-acting formulation.


When properly treated, diabetes insipidus does not reduce life expectancy. However, symptoms may not be able to be completely eliminated even with treatment in individuals with severe forms of the disease.

Diabetes mellitus has long-term complications. It doubles the risk of cardiovascular disease, stroke and peripheral vascular disease, as well as chronic kidney disease. The life expectancy of someone with Type 2 diabetes is up to 10 year shorter than someone without type 2 diabetes.

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