Blood Osmolality Test

Blood Osmolality Test Definition:

The term “blood” refers to all types of red cells (RBC) and platelets (PRL). RBC are the body’s main source of oxygen and they carry oxygen throughout your body. Platelets are special white blood cells which play a major role in fighting infections such as colds, flu, etc. They help destroy germs and other foreign substances from inside the human body.

Oxygenated blood contains approximately 3 times more hemoglobin than nonoxygenated blood. Hemoglobin is a protein found in red blood cells. Oxygen binds with hemoglobin and allows it to transport oxygen throughout the body. Without oxygen, hemoglobin would not work properly and the cell would die.

Hematocrit or haemoglobin concentration determines how much oxygen is carried into the tissues of the body. A low haemoglobin level indicates that the tissue is deprived of oxygen. High haemoglobin levels indicate that there is adequate oxygen supply to the tissues.

In addition to these two components, blood contains platelets which help prevent bleeding in cases of trauma or surgery. Blood clotting factors assist in preventing clots from forming after injury or surgery.

Osmolality is a measure of the concentration of solutes in solution. It is usually measured in terms of particles rather than molarity or mass per volume. Osmotic pressure can be defined as the pressure required to prevent the inward flow of water across a semi permeable membrane, when there is a difference in concentration of sugar or salt solution on either side of the membrane.

Osmolality indicates the number of particles present in a solution, usually expressed in terms of the number of particles per kilogram of water. It is sometimes called the osmolarity of a solution. The more concentrated the particles are in a solution, the higher its osmolality or osmolarity will be.

Urine osmolality test is a lab test that measures the concentration of your urine. Urine osmolality shows how concentrated or diluted your urine is. This can help your healthcare providers determine if you are properly hydrated. It can help rule out other possible conditions and illnesses.

Blood Osmolality Test Preparation.

Usually no preparation is required for this test. However, if you are instructed to do so, you may need to limit your intake of certain foods, drinks, and medicines for 8 to 12 hours before the test.

Blood Osmolality Test – Procedure.

A blood osmolality test requires a blood sample drawn from a vein in your arm. The health professional taking the sample will use a needle to obtain it.

Blood Osmolality Test – Aftercare.

After having the test, you can resume all of your normal activities.

Blood Osmolality Verification – Sample Types.

Verification (also called confirmation) is done when the initial test results are found to be questionable. The tests that may be ordered when the results of the first test are questionable and need verification include chest x-ray, complete blood count, and ESR (erythrocyte sedimentation rate).

Blood Osmolality Normal Values.

Healthy normal blood osmolality range from 280 to 300 mOsm/kg.

Blood Osmolality Test Results.

Test results are usually available immediately or within 24 hours.

If you have had the blood osmolality test before, your most recent and your previous results are compared. This enables your health practitioner to determine if the level of sodium in your blood is rising or falling over time.

A blood osmolality test measures the concentration of particles in a certain volume of blood. It is a simple and noninvasive test that can be done to screen for potential dehydration. It measures the number of particles found in a solution of blood. This test screens for conditions such as Addison’s disease, which causes the body to retain water and leads to low sodium levels (hyponatremia).

A low blood osmolality reading may indicate you are dehydrated. It might also indicate that you have Addison’s disease, if the level of sodium in your blood is low.

A high reading may indicate that you have adrenal or pituitary gland problems, which may lead to high blood pressure (hypertension).

Addison’s disease is an endocrine disorder that occurs when the body does not produce enough of the hormones aldosterone and cortisol. This condition can cause the body to retain water. It can also cause electrolyte imbalances, such as low sodium levels in the blood (hyponatremia).

Addison’s disease may be caused by an autoimmune disorder, surgical removal of the adrenal glands, destruction of the adrenal glands by prolonged acute illness, or it may occur for no known reason.

Addison’s disease can lead to a life-threatening electrolyte imbalance if not detected and treated promptly.

Blood osmolality is a measure of the number of particles found in a solution of blood.

A blood osmolality test is a simple and noninvasive procedure that can be used to screen for conditions that cause the body to retain water.

Prolonged vomiting or diarrhea can also cause dehydration that may result in a low blood osmolality reading.

Blood Urea Nitrogen (BUN)

What Does a Blood Urea Nitrogen (BUN) Test Measure?

Sources & references used in this article:

The role of blood osmolality and volume in regulating vasopressin secretion in the rat by FL Dunn, TJ Brennan, AE Nelson… – The Journal of clinical …, 1973 – Am Soc Clin Investig

The interaction of blood osmolality and blood volume in regulating plasma vasopressin in man by GL ROBERTSON, S ATHAR – The Journal of Clinical …, 1976 –

The effects of blood osmolality changes on cat carotid body chemoreceptors in vivo by R Gallego, C Belmonte – Pflügers Archiv, 1979 – Springer

Hydration testing of athletes by RA Oppliger, C Bartok – Sports Medicine, 2002 – Springer

Controlled water intake: a method for objectively evaluating thirst and hydration state in monkeys by the measurement of blood osmolality by H Yamada, K Louie, PW Glimcher – Journal of neuroscience methods, 2010 – Elsevier

Measurement of whole blood osmolality by MH Weil, S Michaels, D Klein – American journal of clinical …, 1982 –

Survival, blood osmolality, and gill morphology of juvenile yellow perch, rock bass, black crappie, and largemouth bass exposed to acidified soft water by JH McCormick, KM Jensen, RL Leino – Transactions of the …, 1989 – Taylor & Francis