Is Alkaline phosphatase 21 low, normal or dangerous? What does ALP level 21 mean?

📅 Medical Review Date: October 22, 2025

Your Alkaline phosphatase level of 21 is a Low Alkaline phosphatase level.

An alkaline phosphatase level of 21 U/L usually means bone turnover or liver activity is reduced. It suggests possible nutritional deficiencies. Low levels of alkaline phosphatase can cause fatigue, weakness, bone pain, frequent fractures, and poor growth in children. This can be caused by hypophosphatasia, malnutrition, Wilson's disease, or hypothyroidism. Further tests are often needed to identify the cause and guide appropriate treatment.

Low Alkaline phosphatase levels may indicate underlying health problems. The normal range is typically between 30 U/L and 120 U/L. If your levels are outside this range, it's important to speak with a healthcare provider. Consulting a doctor is recommended to determine the cause and appropriate next steps.

The normal Alkaline phosphatase range for men is :30 - 120 U/L

Ideal values of Alkaline phosphatase depending on age (male) :

Age	Ideal Alkaline phosphatase value
<5 years	30.63
5-10 years	31.273
10-15 years	31.93
15-20 years	32.601
20-25 years	33.286
25-30 years	33.985
30-35 years	34.699
35-40 years	35.428
40-45 years	36.172
45-50 years	36.932
50-55 years	37.708
55-60 years	38.5
60-70 years	39.309
70-80 years	40.134
80-90 years	40.977
90-100 years	41.838
>100 years	42.717

*Ideal values are calculated based on our database of patient records

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1,51,150

Total number of patients treated

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Some examples of conditions that increase or decrease Alkaline phosphatase levels include:

• Alcohol abuse
• Ulcerative colitis
• Blockage of the bile ducts.
• Insulin resistance
• Congestive heart failure

Receive world-class medical opinion about your low Alkaline phosphatase levels over email.Upload blood test report now

Normal range of Alkaline phosphatase found among women :30-120 U/L

Ideal values of Alkaline phosphatase depending on age (female) :

Age	Ideal Alkaline phosphatase value
<5 years	30.649
5-10 years	31.312
10-15 years	31.989
15-20 years	32.681
20-25 years	33.388
25-30 years	34.11
30-35 years	34.848
35-40 years	35.602
40-45 years	36.372
45-50 years	37.159
50-55 years	37.963
55-60 years	38.784
60-70 years	39.623
70-80 years	40.48
80-90 years	41.356
90-100 years	42.251
>100 years	43.165

If you take a Alkaline phosphatase blood test and the results are not in the normal range (30-120 U/L), your physician may recommend more tests to figure out the problem. You might also get this test if your physician thinks you have some other disease.

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How the Alkaline phosphatase Test Is Done :

When your doctor orders a Alkaline phosphatase test, it involves a straightforward blood draw to measure your Alkaline phosphatase levels. A pathologist or lab technician will take a small sample of blood from a vein using a needle. Your Alkaline phosphatase test results are usually available within a few hours.

Medical References

• Cleveland Clinic – Alkaline Phosphatase (ALP): What It Is, Causes & Treatment
• Mayo Clinic – Alkaline phosphatase (ALP) blood test
• MedlinePlus – Alkaline Phosphatase
• WebMD – Alkaline Phosphatase (ALP): Tests and Results

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