Urea

What is Urea?

Urea is a waste product produced from the breakdown of protein in the liver. When the liver breaks down proteins, nitrogen in ammonia form is produced. The nitrogen then combines with other chemicals in the liver to make urea. Urea is released into the bloodstream where it is transported to the kidneys, filtered out, and excreted from the body via urine^[1][2]. Therefore, urea is a good indicator of how your liver and kidneys are working.

In healthy individuals, urea is cleared from the body rapidly, but in people whose kidney function is impaired, the steady build-up of urea can be toxic. It may also play a role in the development of atherosclerosis^[3].

Why is urea used in skincare products?

Although urea is a byproduct of protein metabolism, it is frequently included in skin cleansers and moisturisers because of its purported moisturising and exfoliating properties. Urea is well tolerated and regulates the number of cells in the epidermis, the outermost layer of skin, called keratinocytes.

Urea is also integral to the skin’s barrier function and for protecting against pathogens. Urea-containing skin formulations have been shown to help promote healthy skin and treat several skin conditions, including psoriasis, seborrheic dermatitis, and atopic dermatitis^[4].

What is a Normal Level?

According to the NHS, a healthy blood urea level ranges from 2.5 to 7.8 mmol/L^[5].

Data collected from Forth customers shows that, on average, urea levels are within the healthy range for all age groups and both sexes.

What Causes a Urea Imbalance?

Serum urea concentration demonstrates the balance between urea production by the liver during amino acid breakdown and its excretion by the kidneys via urine. So, high urea levels in the blood usually signify an increase in urea production, a reduction in urea being filtered out of the blood and removed from the body or a combination of the two.

Often the highest levels of serum urea are because of a reduction in elimination by the kidneys because of kidney disease or a significant reduction in glomerular filtration^[6]. This is called uremia.

There are several other possible causes of high urea levels:

• Dehydration
• Heart failure
• Urinary tract infections
• Gastrointestinal bleeding
• Diabetes
• Lupus
• Some cancers including multiple myeloma
• Haemolytic uremic syndrome
• High blood pressure

Symptoms of high urea

One of the common causes of high blood urea levels is kidney dysfunction or disease which stops the proper elimination of urea (and other waste products) from the body.

The symptoms of high urea levels are:

• Muscle cramps
• Feeling sick
• Being sick
• Fatigue
• Weight loss
• Itchy skin^[7]

Low urea levels

Low blood urea levels are rare and are not usually a concern. Low levels may be seen in severe liver disease or malnutrition but urea levels are not used to diagnose these conditions. It is also normal for pregnant women to have low urea levels.

Symptoms of low urea

The symptoms of low urea are likely to correspond with the underlying cause. For example, if severe liver disease is causing low blood urea, you may experience symptoms such as:

• Tiredness and weakness
• Itchy skin
• Jaundice
• Low libido
• Loss of appetite
• Feeling or being sick^[8]

How to Keep Urea in the Healthy Range

If you have chronic kidney disease you may require treatment such as dialysis to help filter your blood and remove waste products from your body.

There are certain lifestyle choices you can make to reduce your risk of developing high blood urea levels. They include:

• Controlling diabetes: Diabetes is the world’s most common cause of kidney disease, so keeping your blood sugar levels in check, can reduce your risk^[9].
• Maintain healthy blood pressure: High blood pressure is a cause of chronic kidney disease^[10] and kidney disease can increase your blood pressure^[11]. So, it is important to take steps to keep your blood pressure within a healthy range, such as eating a healthy diet, eating less than 6g of salt per day, losing weight, cutting down your caffeine intake, and quitting smoking.
• Quit smoking: Cigarette smoking is a risk factor for developing kidney disease and raises biomarker levels including urea and creatinine^[12].
• Weight loss: A study published in 2007 found that weight loss in obese adults reduced urea production by 25%^[13]. Other studies have found that weight loss can improve the glomerular filtration rate (GFR) in obese adults with chronic kidney disease^[14].
• Follow a good diet and exercise plan: There is some evidence to suggest that high-protein diets may harm kidney function^[15]. This is particularly relevant for anyone who may be at a greater risk of developing kidney disease. Anyone who eats a large quantity of protein, perhaps to lose weight or gain muscle, is likely to be producing high levels of urea. Some research suggests that a Mediterranean Diet may help to prevent the development of chronic kidney disease and maintain kidney function^[16]. Exercise has also been shown to improve kidney function, but also regulate blood pressure, maintain energy balance, and aid weight loss. Aerobic exercise, resistance training, or a mixture of both have positive benefits for kidney disease patients^[17].

Can drinking water lower urea?

Dehydration can increase serum urea levels, so drinking water may help to bring them back within a normal range. A study published in 2010 found that drinking 25 ml/kg of water in 24 hours reduced serum urea levels by 40%^[18].

What foods cause high urea?

A diet that is high in protein may increase urea and other nitrogen-based waste products in the blood. These include foods like:

• Meat
• Fish
• Dairy products (milk, cheese, yogurt)
• Eggs

Written by Leanne Edermaniger

Based in the UK, Leanne specialises in writing about health, medicine, nutrition, and fitness.

She has over 5 years of experience in writing about health and lifestyle and has a BSc (hons) Biomedical Science and an MSc Science, Communication and Society.