7 Causes of Slightly Elevated Alkaline Phosphatase (160, 170, 180, 200 U/L, etc.)

A slightly elevated alkaline phosphatase level is caused by either physiological conditions (such as pregnancy, growing bones, or aging). It is also caused by disease conditions such as liver, biliary, bone, thyroid diseases, some cancers, etc.

The normal reference range of alkaline phosphatase in adult males and females is between 44 and 121 U/L (reference).

Slight variations between labs in the reference ranges are often present. Check the normal reference range provided by your lab.

Slight alkaline phosphatase (ALP) elevations refer to values just above the upper limit of normal (150, 160, 170, 180 U/L, etc.

Also, ALP values up to twice the upper limit of normal (121*2 = 242) are considered slight elevations.

The marked elevation is a term that describes alkaline phosphatase levels that are more than 4 or 5 times the upper limit of normal.

The table below summarizes the causes of slightly elevated alkaline phosphatase levels ( 160, 170, 200, or up to twice the upper limit of normal) (reference).

Physiological causes of slightly elevated alkaline phosphatase.

1. People with blood groups (B) or (O).

The alkaline phosphatase is an enzyme in a wide variety of tissues. Commonly, it is found in bones and the liver.

Also, the gastrointestinal tract (particularly the small intestine) is abundant in ALP.

Normally, the intestinal alkaline phosphatase enters the bloodstream after eating. But it rapidly binds to your red blood cells, so its levels do not increase.

NOTE: blood tests detect ALP that is free in the bloodstream (serum), not the ALP bound to red blood cells.

In people with blood groups (B) and (O), the red blood cells are less capable of binding the intestinal ALP reaching the bloodstream.

As a result, those people may experience slight elevations in serum alkaline phosphatase after eating.

The elevations are more noticeable after eating high-fat foods. And the levels often return to normal after they eat.

Symptoms & diagnose:

The condition is completely benign without any symptoms.

To diagnose your condition, your doctor will fulfill the following criteria:

• Absence of symptoms of liver, biliary, and bone disease.
• Isolated ALP increases (other lab tests are normal such as liver enzymes, bilirubin, etc.).
• Repeat testing while fasting (ALP often returns to normal).

The elevation in ALP is often mild (160-200). However, it may reach more than 300 U/L (reference).

2. Growing infants, children, and young adolescents.

Alkaline phosphatase is present in abundance in bones. Therefore, alkaline phosphatase often increases during bone growth and bone formation.

That’s why the reference ranges of alkaline phosphatase vary significantly in children and adolescents.

A slight elevation in ALP is normal in infants, children, and growing adolescents.

The chart below illustrates the significant differences in infants, children, and adolescents compared to the adult levels (reference).

3. Aging.

People who get older (often those in their 50s, 60s, and older) have slightly elevated alkaline phosphatase levels (reference).

Slight elevations of alkaline phosphatase such as 160 or 170 U/L can result from advancing in age.  

4. Pregnancy.

Alkaline phosphatase is found in the placenta. Therefore, you may experience slight enzyme elevations during pregnancy during the first two trimesters.

In the third trimester, alkaline phosphatase levels rise significantly due to the presence of a fully-formed large placenta.

The upper limit of normal alkaline phosphatase is up to twice that of normal (121 in non-pregnant adults).

The rise is completely asymptomatic. And doesn’t need any further investigations in the third trimester unless:

• The rise is more than twice the upper limit of normal.
• You have symptoms such as severe itching, yellowish skin or eye whites, or right upper abdominal pain.

The chart below shows the average alkaline phosphatase levels during pregnancy (reference). Note the significant rise during the third trimester.

5. Some medications.

Certain medications may affect the alkaline phosphatase levels and cause either slight or marked elevations in alkaline phosphatase.

The rise in alkaline phosphatase is mainly due to the medications that cause bile stasis (drug-induced cholestasis).

Examples include (reference):

• Some antibiotics such as ampicillin, erythromycin, and other penicillin-based antibiotics.
• Oral contraceptive pills.
• Chlorpromazine.
• And others.

Tell your doctor about any recent or chronic medication use if you have slightly elevated alkaline phosphatase levels (such as 160, 170 U/L, or more).

7. Unexplained.

Any physiological or disease cannot explain some slightly isolated alkaline phosphatase cases.

The rise is often mild, isolated, with otherwise normal enzymes.

In such cases, your doctor may require follow-up testing for the enzymes (often after a few weeks or months).

Diseases causing slightly elevated alkaline phosphatase levels.

1 . Diabetes mellitus.

Diabetes is one of the most common diseases worldwide. According to the WHO (World health organization), about 8.5% of adults have diabetes.

Studies found that alkaline phosphatase is slightly elevated in patients with diabetes compared to non-diabetic patients (reference).

Slightly elevated ALP levels (such as 160 or 170 U/L) can occur in patients with diabetes.

The exact cause is not fully understood. However, research attributes the rise to the effect of diabetes on the bone (diabetic bone disease) and non-alcoholic fatty liver disease.

2. Bone diseases.

Many bone diseases can cause slight to moderate elevations in alkaline phosphatase.

The most common examples include (reference):

• During the healing of bone fractures (particularly the first few weeks).
• Osteomalacia (often due to severe vitamin D deficiency).
• Paget’s disease of bone.
• Hyperthyroidism.
• Hyperparathyroidism.
• Bone cancer (osteosarcoma).
• Bone Mets (cancer spread to the bones).

Patients with slight elevations of alkaline phosphatase often have symptoms of bone affection such as:

• Bone pain (localized in cancer, widespread in osteomalacia).
• Easy fractures.
• Bone mass (hard swelling).
• Symptoms of the primary cause such as hyperthyroidism, cancer, etc.).

3. Liver  & biliary diseases.

Diseases obstructing the bile outflow from the liver often cause marked elevations in alkaline phosphatase.

For example, gallstones obstructing the common bile duct may cause alkaline phosphatase levels of more than 500 or 600 U/L.

On the other hand, other liver disease causes only mild or partial bile stasis. In addition, this disease often causes minimal rises in alkaline phosphatase.

Common liver diseases that cause slightly elevated ALP (reference):

• Alcoholic hepatitis.
• Acute and chronic viral hepatitis (Hepatitis A, B, C, D, etc.).
• NASH (non-alcholic steatohepatitis).
• Liver cirrhosis.
• Infiltrative liver diseases such as Tuberculosis, sarcoidosis, amyloidosis, etc.
• Autoimmune hepatitis.
• Liver congestion (often due to heart failure).
• Decreased liver blood supply (hypoperfusion) as with sepsis and septic shock.
• Benign post-operative cholestasis.
• Gilbert’s syndrome.
• Liver abscess.

4. Certain cancers.

Cancers may cause mild (slight) to moderate increases in alkaline phosphatase levels. Different mechanisms of cancer-induced elevations in alkaline phosphatase include:

• Secretion of excess alkaline phosphatase by cancer cells (especially in patients with Hodgkin’s lymphoma)
• The cancer spread to the liver
• The cancer spread to bones
• Cancers that cause a partial block in the bile ducts

Common cancers associated with mild to moderate elevations include (reference):

• Hodgkin’s lymphoma.
• Liver cancer.
• Breast cancer.
• Bone cancer (primary or metastatic).
• Head and neck cancers.
• Ovarian cancer.
• Uterine cancer.
• Kidney cancer (renal cell carcinoma).
• Stomach (gastric) cancer.
• Lung cancer.

5. Gastrointestinal diseases.

Alkaline phosphatase is present in the cells of the gut tract (mainly the small intestine, stomach, and colon).

Some diseases of the gastrointestinal tract may cause slightly elevated alkaline phosphatase levels, such as (reference):

• Stomach ulcers (uncomplicated).
• Perforated bowels.
• Intestinal infarction (mesenteric vascular occlusion).
• Stomach cancer.
• And others.

6. Kidney diseases.

Patients with kidney failure, chronic kidney disease, or cancer often have elevated alkaline phosphatase levels (reference).

The elevation can be slight or moderate to marked, depending on the severity of the disease.

7. Thyroid diseases.

A disease that causes hyperactive thyroid gland leads to slight elevations of the alkaline phosphatase level.

Examples include (reference):

• Hyperthyroidism.
• Subacute thyroiditis.

The effect of excess thyroid hormones on bones is why alkaline phosphatase rises with hyperactive thyroid disease.

8. Others.

Other possible causes of slightly elevated alkaline phosphatase levels include (reference):

• Acromegaly (increased growth hormone levels in adulthood).
• Leukemia.
• Myelofibrosis.
• Myeloma (rarely).
• Hypervitaminosis D.
• Pseudohypoparathyroidism (a rare genetic disease in which the body tissues are unresponsive to the parathyroid hormones).
• Fanconi syndrome.
• Congestive heart failure.
• Familial hyperphosphatemia.

When to see a doctor for a slightly elevated alkaline phosphatase?

Many physiological conditions cause a slight rise in ALP levels (such as early childhood, adolescence, pregnancy, etc.). These conditions often don’t require further investigations or workup as long as you don’t have other symptoms or lab derangements.

See the doctor if:

• The rise of alkaline phosphatase is not explained by the physiological conditions explained above.
• Symptoms of liver affection include jaundice, upper right quadrant pain, itching, swollen limbs, etc.
• Symptoms of bile obstruction include jaundice, dark urine, clay stools, and severe biliary colics.
• Unexplained itching.
• Unexplained abdominal pain.
• Taking medications that cause an elevation in alkaline phosphatase.
• Unexplained fever or weight loss.
• Widespread or localized bone pain.
• Neck mass or symptoms of hyperactive thyroid (sweating, fever, tremors, irritability, diarrhea, progressive weight loss, and hunger).