Ray Peat on Urea

January 29, 2026

The Decline of Urea Use in the Treatment of Brain Injuries

As late as the 1950s, urea was considered the most effective treatment for brain swelling. However, the scientifically based membrane theory assumed that water removal from cells was always determined by osmosis – and since urea could remove water from cells, it had to be osmotically active. As an osmolyte, it was added to distilled water for intravenous use, and red blood cells behaved as they do in distilled water: they dissolved. The report that urea causes hemolysis eventually led to its general discontinuation in the treatment of brain injuries.

March 2020 - Ray Peat's Newsletter

Positive Effects of Various Substances in Healthcare

Like intracellular ATP, an adequate amount of progesterone, T3, urea, and carbon dioxide each have an infinite variety of positive effects – individually and in combination. Together with their synergistically acting nutritional, botanical, and pharmaceutical substances, their application could fundamentally change healthcare.

March 2020 - Ray Peat's Newsletter

The Lost Role of Urea in Brain Treatment

Fifty years ago, urea was widely used to treat brain injuries, but a misunderstanding of its physical properties – and today the availability of highly profitable vaptans – have displaced it.

March 2016 - Ray Peat's Newsletter

Carbon Dioxide and Lactate Dynamics in Cellular Processes

While the flow of carbon dioxide from the mitochondrion into the cytoplasm and beyond tends to remove calcium from the mitochondrion and the cell, the influx of lactate and other organic ions into the mitochondrion under conditions where carbon dioxide synthesis – and consequently urea synthesis – is reduced and other synthesis processes are altered, can lead to an accumulation of calcium in the mitochondrion.

July 2000

The Unique Osmotic Balance of Sharks Through High Urea Concentration

Sharks are – aside from being primitive and not suffering from cancer – also physiologically unique in another way: their body fluids are osmotically balanced with seawater, making them hypertonic compared to the body fluids of other animals. The mineral content in shark blood does not differ much from that of other animals. The osmotic difference is balanced by a very high concentration of urea (and trimethylamine).

July 1991 - Ray Peat's Newsletter

PMS, Edema, and Historical Treatments

Edema is a common problem in PMS, and it was once thought that brain edema was responsible for irritability, depression, or other nervous symptoms; therefore, diuretics such as ammonium compounds and urea were frequently used. (The premenstrual craving for salt is the result of estrogen-disrupted water balance, and salt restriction in PMS is as inappropriate as in preeclampsia or toxemia of pregnancy.)

July 1991 - Ray Peat's Newsletter

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