“Diabetes” is a Greek word meaning siphon — to empty by. Diabetes mellitus and diabetes insipidus are distinct conditions which share some symptoms and the first word of their name.

Diabetes insipidus is a condition where the kidneys are unable to keep water in the body, so it is passed as large amounts of urine. Diabetes mellitus, commonly known as diabetes, is a condition of high blood glucose (sugar) levels that occurs when the body produces little insulin, or does not respond well enough to the insulin in the blood.

Diabetes insipidus is a rare condition that affects 1 in 25,000 people worldwide, while diabetes mellitus is more common and affects 1 in 11 adults worldwide.

Causes of diabetes insipidus Vs diabetes mellitus

Causes of diabetes insipidus

Vasopressin, or antidiuretic hormone (ADH), is a hormone produced by your hypothalamus then stored and produced by your pituitary gland. ADH mainly controls the amount of water your kidneys retain as they filter your blood to remove waste products and minerals.

The hypothalamus is a part of your brain that controls the activity of your pituitary gland and the section of your nervous system not under conscious control (the autonomic nervous system). The pituitary gland is located at the base of the brain, just below the hypothalamus. It makes, stores and releases many important hormones.

There are 4 types of diabetes insipidus (DI):

1. Central DI: Here, you don’t have enough ADH in the body because of damage to the hypothalamus or the pituitary gland. In many cases of central DI, there may be no identified cause. Known causes include brain tumors, head injury, surgery, infections of the brain or autoimmunity, where the immune system attacks cells that make ADH.
2. Nephrogenic DI: Where you have enough ADH in the body, but your kidneys do not respond to it properly. It may be caused by:
   • Kidney infections (pyelonephritis)
   • Low blood potassium levels (hypokalemia)
   • High blood calcium levels (hypercalcemia)
   • Long-term use of some medications, such as lithium
   • Chronic kidney disease
   • Obstruction to urine flow
   • Certain genetic mutations

1. Primary polydipsia: It is unrelated to ADH, but you drink a lot of liquids and urinate often. It may be caused by certain mental disorders or a problem with the thirst mechanism in the brain.
2. Gestational DI: This is a condition that can develop during pregnancy. It happens when a certain hormone from the placenta that breaks down ADH has higher than normal levels in the blood.

Causes of diabetes mellitus

The causes of diabetes mellitus (DM) depend on the type you have. There are 3 main types of DM:

1. Type 1 diabetes: Here, the body produces little or no insulin. Because of unknown triggers, your immune system attacks the cells that make insulin. It is also associated with having certain genes.
2. Type 2 diabetes: The cells in your body do not respond well to insulin. It is a complex condition that is caused by interaction of having certain genes, obesity, reduced physical activity, hormonal issues and long-term use of certain medications like corticosteroids and albuterol.
3. Gestational diabetes: It is a condition of high blood sugar levels during pregnancy, caused by increased release of certain hormones from the placenta. The hormones affect the response of cells to insulin in the body.

Symptoms of diabetes insipidus Vs diabetes mellitus

These conditions share some similar symptoms, even though the causes of the symptoms may differ. These symptoms are:

• Excessive urination. This shared symptom is the reason DI and DM share a common first word. But in DI, the kidneys are unable to retain water in the body, so it is passed out as large amounts of dilute urine; up to 20 quarts (about 19 liters) of urine in a day. In DM, the kidneys will produce much urine as they try to flush excess glucose out of the body.
• Thirst. In both conditions, you become thirsty because you are losing so much water.
• Blurry vision. In DI, prolonged dehydration will blur your vision. In DM, high blood sugar will alter the ability of your eyes to focus on objects.
• Fatigue. In DI, it may be caused by dehydration and imbalance of electrolytes like sodium and potassium. In DM, it is usually caused by too high or too low blood sugar levels.

DM may have many unique symptoms other than the ones above. Some common ones include:

• Sores or cuts that heal slowly
• Dry, itchy skin
• Numbness and tingling in the hands or feet
• Frequent skin infections
• Unintended weight loss

Diagnosis of diabetes insipidus Vs diabetes mellitus

Diagnosing DI

A number of tests can be done to determine whether you have DI, and what type it is. The tests may include:

1. Blood tests

A medical professional collects one or more samples from your vein. The blood may be tested for:

• The levels of ADH.
• The sodium levels. You may have DI if your blood sodium levels are higher than normal.
• The concentration of particles in the blood (serum osmolality). Normal serum osmolality is 275-295 milliosmoles per kilogram(mOsm/kg). Serum osmolality higher than 295mOsm/kg may mean you have DI.
• Urine tests

You may be required to collect all the urine you pas within 24 hours. If the total urine amount is higher than normal, you may have DI.

Urinalysis is a test that can be done to check for the appearance, content, and concentration of your urine. In this test, you will be told to pee in a urine collection bottle. A urinalysis will then be done to determine the urine osmolality (concentration of particles in urine).

1. Water deprivation test

This involves not drinking any liquid for several hours and monitoring how your body responds. Normally, you will pass a small amount of concentrated urine as your body tries to conserve water. If you have DI, you will urinate large amounts of dilute urine.

1. Imaging

Magnetic resonance imaging (MRI) can be done to see if there is a problem with your hypothalamus or pituitary gland that may be causing DI.

Diagnosing DM

Tests which can be done to measure your blood sugar levels are:

• Fasting blood glucose test: Your blood sugar level is measured after an overnight fast.
• Random blood glucose test: At any time of the day, your blood sugar is measured. You are not required to fast. This test is used to diagnose DM if you have symptoms.
• A1c test: This test measures your average blood sugar levels over the past 3 months.

Treatment of diabetic insipidus Vs diabetes mellitus

Treating DI

The treatment for DI depends on which type you have.

1. Nephrogenic DI: Removing the cause is an important step in managing the condition. For example, discontinuing the use of lithium or treating kidney infections. Your doctor may prescribe medication to reduce how much urine your kidneys make. These may include thiazide diuretics, and non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen. A low salt diet may also help to reduce the urine volume.
2. Central DI: If you don’t make enough ADH, your doctor may prescribe desmopressin, a medication that works like ADH. Desmopressin can be administered as a shot, pill or nasal spray.
3. Primary polydipsia: If it is caused by a mental disorder, medication may be used to treat the condition. Currently, there is no effective treatment for a defective thirst mechanism. Your doctor may suggest that you such on ice chips to help reduce thirst. A nighttime dose of desmopressin may be helpful if you wake up too many times to pee at night.
4. Gestational DI: It is treated with desmopressin. You may not need treatment after you give birth.

Treating DM

Managing blood sugar levels in people living with DM requires a combination of different treatment options. Treatment may involve:

• Lifestyle changes: Eating a diabetes-friendly diet, being physically active and regularly monitoring blood sugar levels are important components of any diabetes treatment plan.
• Insulin: It is used to control blood sugar levels in people with type 1 diabetes. If you have type 2 diabetes, you may need to receive insulin in addition to oral medications.
• Oral medication: If you have type 2 diabetes, you may need to take one or more oral anti-diabetes medications to manage your condition.

Complications of diabetes insipidus Vs diabetes mellitus

When untreated, these conditions have different effects on your body.

Complications of DI may include:

• Dehydration
• Growth retardation in children
• Low blood pressure (hypotension)
• Brain damage
• Kidney damage

Complications of DM may include:

• Nerve damage
• Kidney disease
• Heart disease
• Eye disease
• Stroke
• Diabetic ketoacidosis (DKA), a condition that usually happens in people living with type 1 diabetes where substances called ketones accumulate in blood and make it acidic.

Can I have diabetes insipidus and diabetes mellitus at the same time?

Even though it is extremely rare, you can have DI and DM at the same time. This is what happens in a rare genetic condition called Wolfram syndrome, where you have both conditions, visual problems and hearing problems. Rare cases have been reported where people have DI and DM without having Wolfram syndrome.

What should I remember?

Diabetes insipidus and diabetes mellitus are distinct conditions, despite sharing the name “diabetes.” Diabetes insipidus involves an imbalance in the body’s water regulation, leading to excessive thirst and urination. It is caused by issues with the hormone vasopressin or the kidneys’ response to it, not by blood sugar levels.

Understanding the differences between these conditions is important for proper diagnosis and treatment. While diabetes mellitus is managed by controlling blood sugar, diabetes insipidus requires addressing fluid balance. Recognizing symptoms early and seeking appropriate care can help manage both conditions effectively.