Alkaline Phosphatase (ALP)

What is Alkaline Phosphatase (ALP)?

Alkaline phosphatase is an enzyme that breaks down protein and is involved in bone development, and metabolism. Around 80% of the ALP found in the blood comes from the liver and bone^[1], but it is also found in smaller amounts in the intestines, kidneys, and placenta in pregnant women.

Different forms of ALP circulate in the body, depending on where they come from. These are called isoenzymes.

The 4 isoenzymes are:

1. Intestinal ALP

2. Placental ALP

3. Germ cell ALP

4. Tissue nonspecific ALP or liver/kidney/bone ALP^[2]

In most cases, raised ALP levels are a sign of bone or liver problems. Further biomarkers will need to be analysed to distinguish between the two. For example, an increased ALP level and:

• High bilirubin, gamma-glutamyl transferase (GGT) or alanine aminotransferase (ALT) usually indicates liver dysfunction.

• Abnormal calcium and phosphate levels suggest the ALP may be derived from bone.

High levels of ALP are likely during pregnancy because of placental growth. In these cases, the usual reference ranges do not apply. ALP levels are dependent on the size of the placenta.

What is a Normal Level?

The NHS states that the normal reference range for adults is 30 to 130 units per litre (U/L). In children and teenagers, it is not uncommon for their ALP ranges to be 3 to 4 times the level of the adult range because of bone growth during this time^[3].

Our data shows that the average ALP level is 69.6 IU/L for women and 74.9 IU/L for men.

Average alkaline phosphatase levels by Forth customer’s age are as follows:

Age Group	Average ALP Levels by Age (IU/L)
18-29	75.9
30-39	70.5
40-49	68.6
50-59	72.5
60+	78.8

What level of alkaline phosphatase is dangerous?

Very high levels of alkaline phosphatase levels are more than 1000 U/L. These levels are typically seen in people with sepsis and cancer. Sepsis causes normal bilirubin levels but elevated ALP levels^[4].

However, ALP levels above the normal reference range of 130 UI/L are considered high and are likely to require further investigation to rule out liver or bone disease.

Who Should Test Their ALP?

An ALP test is usually used to monitor liver function or analyse bone health. You may need an ALP test if you are experiencing liver or bone symptoms.

People who drink a large amount of alcohol may want to test their ALP levels alongside other common liver function biomarkers, specifically gamma-glutamyl transferase or GGT.

To understand how ALP may be affecting you, it may be useful to measure these additional biomarkers:

• Liver Health: Alanine aminotransferase (ALT) & GGT
• Bone Health: Vitamin D

You can check your ALP levels with the following at-home test kits from Forth:

• Liver Function Blood Test
• Baseline Health Check
• Ultimate Health Check

What Can Cause Alkaline Phosphatase To Change?

ALP levels in the blood can fluctuate at different stages of life, For example, they are elevated during childhood and adolescence when bone growth occurs, but they also peak again as we age. This is reflected in the average levels collected from Forth customers.

Raised ALP levels are most often associated with liver (fatty liver disease, cholestasis, viral hepatitis) or bone disease (Paget’s disease, rickets, osteomalacia) but they may also be a sign of:

• Bile duct blockages caused by gallstones, infections, and sometimes cancer

• Vitamin D deficiency

• Recent bone fracture

• Some cancers e.g. bone, sarcoma

• Diabetes

• An overactive thyroid (hyperthyroidism)^[5][6]

What does low ALP mean?

Low ALP levels are not common but may be caused by certain medications, poor nutrition or thyroid disease.

Some of the causes of low ALP levels are:

• Zinc deficiency

• Pernicious anaemia

• An underactive thyroid (hypothyroidism)

• Hypophosphatasia (a rare inherited condition causing abnormal mineralisation of bones and teeth)^[7]

• Medicines such as oestrogen replacement therapy in postmenopausal women and the oral contraceptive pill^[8]

The symptoms of low ALP levels will vary depending on the cause. Some common causes and their symptoms can be found in the table below.

Symptoms of high & low

High alkaline phosphatase levels can be a sign of fatty liver disease. Fatty liver disease, commonly known as non-alcoholic fatty liver disease (NAFLD), is a condition where there is a build-up of fat in the liver that’s not caused by alcohol. It is thought that around 1 in 3 people in the UK have the early stages of NAFLD, and it usually affects people who are overweight or obese.

Symptoms include:

• A dull aching pain in the top right of your tummy

• Unexplained weight loss

• Extreme tiredness

• Weakness^[10]

Other symptoms of high ALP causes:

Liver disease	Bone disease
Tiredness/fatigueLoss of appetite Low libidoItchy skin Yellowing skin and whites of the eyes (jaundice) Feeling or being sick[11]	Bone pain Frequent fractures Warm skin over the affected bone Changes in bone shape Tooth issues[12]

Symptoms of low ALP causes:

Zinc deficiency	Loss of taste or smell Hair loss Slow wound healing Rough skin or rashes Deformed nails Lethargy[13]
Hypothyroidism	Tiredness Weight gain Constipation Mood changes Muscle aches, weakness and cramps Dry scaly hair and skin Sensitivity to cold temperatures[14]
Pernicious anaemia	Fatigue Weight loss Headaches Confusion Memory issues Numbness Mood changes Diarrhoea reduced appetite[15]

How to Keep Alkaline Phosphatase in the Healthy Range

If you have raised ALP levels, you may need to speak to a doctor to determine the exact cause or rule out any underlying medical conditions. However, there are things you can do to help support your liver.

Diet

Eating a healthy, balanced diet rich in whole foods, like fruits, vegetables and whole grains can limit the amount of ‘bad’ fat you eat, particularly cholesterol. Although cholesterol is needed for certain functions and processes in the body, large quantities can contribute to the development of non-alcoholic fatty liver disease^[16].

Exercise

Exercise is important for all aspects of health and well-being, but it is particularly beneficial for NAFLD. Research shows that aerobic and strength training can help to lower the amount of fat in the liver, and improve fatty acid metabolism and insulin resistance^[17].

The NHS recommends that all UK adults should aim to complete 150 minutes of moderate-intensity or 75 minutes of vigorous exercise each week, spread out over 4 to 5 days^[18].

Weight loss

Weight loss can benefit people with a fatty liver as it can improve outcomes and reduce the severity of the disease. Being overweight also increases the chance of gallstones but rapidly losing weight can also increase this risk. Therefore, losing weight gradually (less than 2 lbs or 1kg per week) can prevent gallstone formation.

Sunlight exposure

High ALP levels may be caused by low vitamin D levels^[19]. It is important to get some sunlight exposure between March and October by spending 15 minutes per day in the sun to keep your vitamin D levels topped up.

Quit smoking

Smoking is associated with high alkaline phosphatase levels and may increase the damaging effects of alcohol on liver cells^[20].

How to reduce ALP levels quickly

There may not be a ‘fast’ way to reduce raised ALP levels, especially as rapid weight loss can also have adverse effects. However, addressing your lifestyle and making improvements, such as those mentioned above, can help to support your liver health, and help to bring your levels back to within a normal range^[21].

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.