--- title: "High Alkaline Phosphatase in Children: 3 Labs for Rickets" description: High alkaline phosphatase can be normal in growing children—but low phosphorus may signal rickets or another bone disorder. Learn 3 labs that matter. image: https://lifeendo.com/hubfs/high-alkaline-phosphatase-children-rickets-bone-health.png --- [![LIFE\_Pediatric\_CBP\_white](https://lifeendo.com/hs-fs/hubfs/LIFE_Pediatric_CBP_white.png?width=477&height=111&name=LIFE_Pediatric_CBP_white.png "LIFE_Pediatric_CBP_white")](https://lifeendo.com/) [![LIFE\_Pediatric\_CBP\_full\_color.](https://lifeendo.com/hs-fs/hubfs/LIFE_Pediatric_CBP_full_color..png?width=477&height=111&name=LIFE_Pediatric_CBP_full_color..png "LIFE_Pediatric_CBP_full_color.")](https://lifeendo.com/) - [About](https://lifeendo.com/about) - [Meet Your Providers](https://lifeendo.com/about) - [Locations](https://lifeendo.com/locations) - [FAQ](https://lifeendo.com/faq) - Services ### General Endocrine Care - - Early Puberty - Poor Growth - Thyroid Problems - - Type 1 Diabetes - Adrenal insufficiency - Congenital Adrenal Hyperplasia Medical Weight Loss [Visit The Store](https://lifeendo.com/redirecting-to-supplement-store) - [Blog](https://lifeendo.com/blog) - [Patients](https://lifeendo.com/patients) - [Store](https://lifeendo.com/redirecting-to-supplement-store) [Inquire Here](https://lifeendo.com/contact-weight-loss) [Inquire Here](https://lifeendo.com/contact) - [About](https://lifeendo.com/about) - [Locations](https://lifeendo.com/locations) - [Medical Weight Loss](https://lifeendo.com/medical-weight-loss) - [FAQ](https://lifeendo.com/faq) - [Blog](https://lifeendo.com/blog) - [Patients](https://lifeendo.com/patients) - [Store](https://lifeendo.com/redirecting-to-supplement-store) [Inquire Here](https://lifeendo.com/contact-weight-loss) [Bone Disease](https://lifeendo.com/blog/tag/bone-disease) # High Alkaline Phosphatase in Children: 3 Labs for Rickets [![Dr. Kelli Davis](https://lifeendo.com/hs-fs/hubfs/Kelli%20Davis.png?width=40&height=40&name=Kelli%20Davis.png)](https://lifeendo.com/blog/author/dr-kelli-davis) by [Dr. Kelli Davis](https://lifeendo.com/blog/author/dr-kelli-davis) 8 min read Oct 5, 2026 # High Alkaline Phosphatase in Children: 3 Labs That Can Reveal Rickets and Other Bone Disorders **By Kelli Davis, MD | Pediatric Endocrinologist, LIFE Pediatric Endocrinology** When a child’s bloodwork shows a high alkaline phosphatase level, it can look alarming. But in children, **high alkaline phosphatase does not necessarily mean something is wrong.** Children are not small adults when it comes to laboratory testing. Their bones are actively growing, and alkaline phosphatase (ALP)—an enzyme associated with bone formation—is normally much higher during periods of rapid growth than it is in adulthood. ALP levels can rise again around puberty as skeletal growth accelerates.\[1,2\] The more important question isn’t simply: **“Is my child’s alkaline phosphatase high?”** It’s: **“Is it appropriate for my child’s age and stage of growth—and what do the other labs show?”** New research published in *Frontiers in Endocrinology* in September 2026 highlights just how valuable that distinction can be. Researchers found that two relatively common laboratory measurements, **alkaline phosphatase and phosphorus,** could help identify children who may need further evaluation for rickets and other disorders of bone mineralization.\[1\] For parents, there are three laboratory tests worth understanding. ## 1. Alkaline Phosphatase (ALP) Alkaline phosphatase is an enzyme found in several tissues, particularly the **bones and liver**. In growing children, much of the circulating ALP can come from bone. That’s why an ALP result that would appear abnormally high in an adult may be completely appropriate in a child. ### Why Is Alkaline Phosphatase Higher in Children? Growing bones are constantly being remodeled and mineralized. Osteoblasts—the cells involved in building bone—produce alkaline phosphatase as part of that process. ALP levels therefore change throughout childhood. Levels are particularly high during infancy and can increase again during the pubertal growth spurt. Pediatric research demonstrates substantial variation in ALP according to **age and sex**, which is why pediatric reference ranges matter.\[2\] ### Does High Alkaline Phosphatase Mean a Child Has Rickets? **No.** A high ALP level by itself does not diagnose rickets. It can reflect normal skeletal growth, but ALP may also rise in conditions affecting bone mineralization and in some liver and other diseases.\[3\] What matters is **how elevated it is for that particular child and what is happening with the rest of the laboratory and clinical picture.** That’s where the second lab becomes particularly important. --- ## 2. Phosphorus (Phosphate) Phosphorus doesn’t get nearly as much attention from parents as vitamin D or calcium. But it is essential for building and mineralizing healthy bones. And just like alkaline phosphatase, **phosphorus has to be interpreted differently in children than in adults.** Normal phosphorus concentrations are generally higher in infants and younger children and decline toward adult levels with age. Using an adult reference range can therefore cause a genuinely low phosphorus level in a child to be overlooked.\[4\] This is exactly what makes the new 2026 research interesting. ### What Did the New Study Find? Researchers reviewed **45,923 measurements from 12,513 children** younger than 18.\[1\] They specifically looked for the combination of: **Low phosphorus for age + elevated alkaline phosphatase for age.** Among laboratory tests in which both measurements were available, 55 tests from 37 children simultaneously met the researchers’ thresholds of phosphorus below −2 standard deviations and ALP above +2 standard deviations. When those children’s medical records were reviewed, **15 of the 37 had a bone-mineral metabolism disorder.**\[1\] Those diagnoses included: - Nutritional rickets - Osteopenia of prematurity - Osteoporosis associated with ReNU syndrome - A pathogenic *PHEX* variant associated with hypophosphatemic disease Importantly, the strategy uncovered **one previously unrecognized case of mild nutritional rickets.**\[1\] That does **not** mean low phosphorus plus high ALP diagnoses rickets. The study was retrospective and performed at a single center, and the investigators could not determine the sensitivity, specificity or predictive value of the approach. Most children flagged by the laboratory rule did not have rickets. Instead, the study suggests something more practical: > **Routine laboratory results may contain an overlooked clue that a child’s bone metabolism deserves a closer look.** --- ## 3. 25-Hydroxyvitamin D \[25(OH)D\] If rickets or abnormal bone mineralization is suspected, another important test is **25-hydroxyvitamin D**, often written as **25(OH)D**. This is the primary blood test used to assess the body’s vitamin D stores. Vitamin D helps the body absorb calcium and phosphorus, both of which are necessary for normal bone mineralization. Severe or prolonged vitamin D deficiency can contribute to nutritional rickets. But there is an important distinction: ### Rickets and Vitamin D Deficiency Are Not the Same Thing Not every child with low vitamin D has rickets. And **not every child with rickets has low vitamin D.** Rickets can result from several different abnormalities involving calcium, phosphorus, vitamin D metabolism, kidney handling of phosphate and, in some cases, genetic conditions.\[5\] For example, X-linked hypophosphatemia (XLH) is caused by pathogenic variants involving the *PHEX* gene and is characterized by renal phosphate wasting. That’s why simply checking a vitamin D level doesn’t provide the entire picture. --- # The Pattern Matters More Than Any One Number If there is one thing parents should take away from this research, it’s this: **No single laboratory value diagnoses rickets.** A high alkaline phosphatase level can be normal in a growing child. Low phosphorus has to be evaluated using a child’s appropriate reference range. And vitamin D is only one part of bone mineral metabolism. When we evaluate a child, we’re looking at how these findings fit together: **ALP + phosphorus + vitamin D + the child’s growth + symptoms + examination + history.** Sometimes that pattern tells us everything is appropriate for the child’s stage of growth. Other times, it tells us we need to look deeper. --- # What Happens If These Labs Are Abnormal? These three tests are **not a complete rickets workup.** When the initial laboratory pattern or a child’s symptoms raise concern, additional testing may include:\[4,5\] **Calcium** — necessary for normal skeletal mineralization. **Parathyroid hormone (PTH)** — helps determine how the body is regulating calcium and phosphorus. **Creatinine and kidney function** — because the kidneys play a central role in phosphate balance. **Bicarbonate** — certain kidney disorders associated with metabolic acidosis can affect bone health. **Urine phosphorus and creatinine** — can help determine whether the kidneys are inappropriately losing phosphorus. **1,25-dihydroxyvitamin D** — useful in selected disorders of vitamin D or phosphate metabolism. **FGF23** — considered in selected cases of hypophosphatemia, particularly when renal phosphate wasting is suspected. Depending on the findings, imaging or genetic testing may also be appropriate. The important point is that **ALP, phosphorus and vitamin D are clues—not a do-it-yourself diagnostic panel.** --- # When Should Parents Ask About These Labs? Most healthy children do **not** need extensive bone-metabolism testing simply because they are growing. But further evaluation may be appropriate when laboratory abnormalities occur alongside findings such as: - Poor linear growth or declining height percentile - Bone pain or muscle weakness - Bowing of the legs or other skeletal abnormalities - An unusual gait - Widening around the wrists or ankles - Recurrent fractures - Dental abnormalities or recurrent dental abscesses - Nutritional risk factors - Persistently low phosphorus - Alkaline phosphatase that appears unusually elevated for the child’s age and clinical situation Growth failure, skeletal deformities and muscle weakness are among the recognized clinical features that can accompany rickets.\[5\] --- # Why Pediatric Reference Ranges Matter This may be the most important lesson from the entire discussion. **A laboratory result cannot always be interpreted simply because it falls outside the range printed next to it.** Children undergo enormous physiological changes from infancy through puberty. Phosphorus changes with age. Alkaline phosphatase changes with age and sex and rises during periods of rapid skeletal growth.\[2,4\] Even measures used to assess how the kidneys handle phosphorus vary throughout childhood. So when evaluating possible bone or mineral disorders, the question isn’t simply whether a result has an **H** or **L** next to it. The question is whether that result is appropriate **for that child.** --- # The Bottom Line A high alkaline phosphatase level in a child is often related to normal bone growth and does **not** automatically indicate disease. But when ALP is unusually elevated for a child’s age—particularly when it appears alongside **low phosphorus**—it can provide an important clue to an underlying disorder of bone mineralization. Three useful laboratory values to understand are: **1. Alkaline phosphatase (ALP)** **2. Phosphorus (phosphate)** **3. 25-hydroxyvitamin D \[25(OH)D\]** The 2026 study does not establish these as a three-test screening panel for every child. Instead, it reinforces something pediatric endocrinologists see every day: > **The value isn’t simply in ordering a lab. It’s in knowing how to interpret that lab in a growing child.** --- # Frequently Asked Questions ### What Does High Alkaline Phosphatase Mean in a Child? High alkaline phosphatase can be normal in children because ALP is produced during bone growth. Levels vary considerably throughout childhood and can rise during periods of rapid skeletal growth, including puberty. A high result should therefore be interpreted using pediatric age- and sex-appropriate reference ranges and in the context of other laboratory results and symptoms. ### Can High Alkaline Phosphatase Mean My Child Has Rickets? It can be one clue, but **high ALP alone does not diagnose rickets**. Rickets commonly causes elevated ALP, but physicians also evaluate phosphorus, calcium, vitamin D, PTH and other findings when rickets is suspected. ### What Blood Tests Are Used to Check for Rickets in Children? Initial evaluation commonly includes **alkaline phosphatase, phosphorus, calcium, 25-hydroxyvitamin D and PTH**, along with kidney function and other tests depending on the suspected cause. Additional blood, urine, imaging or genetic testing may be necessary. ### What Does Low Phosphorus Mean in a Child? Low phosphorus can have many causes, including inadequate intake or absorption, vitamin D-related disorders and excessive loss of phosphorus through the kidneys. Because normal phosphorus levels are higher in younger children than adults, results should be compared with an age-appropriate pediatric reference range. ### Can a Child Have Rickets With a Normal Vitamin D Level? Yes. Vitamin D deficiency is one cause of rickets, but genetic and phosphate-wasting disorders can cause rickets even when 25-hydroxyvitamin D is normal. ### Is High Alkaline Phosphatase Normal During Puberty? It can be. ALP normally increases during periods of accelerated bone growth, including the pubertal growth spurt. This is one reason adult reference ranges should not be used to interpret ALP in children and adolescents. --- # Concerned About Your Child’s Growth or Bone Health? A single abnormal lab value rarely tells the whole story—especially in a growing child. If your child has **high alkaline phosphatase, low phosphorus, vitamin D abnormalities, poor growth, bone pain, recurrent fractures, or another concern about bone health**, our pediatric endocrinology team can take a closer look at the complete picture. At LIFE Pediatric Endocrinology, we evaluate your child’s **growth pattern, puberty, nutrition, laboratory results and bone health together** to understand what the numbers actually mean—and whether further evaluation is needed. [**Schedule a consultation with LIFE Pediatric Endocrinology →**](https://lifeendo.com/contact) --- # About the Author [**Kelli Davis, MD**](https://lifeendo.com/about-dr-kelli-davis)is a pediatric endocrinologist at **LIFE Pediatric Endocrinology**, a concierge pediatric endocrinology practice caring for children and adolescents through in-person and telemedicine care. Dr. Davis specializes in the evaluation and treatment of pediatric endocrine conditions, including **growth disorders, early and delayed puberty, thyroid disorders, metabolic and bone health concerns, and other hormone-related conditions affecting children and adolescents**. At LIFE, Dr. Davis takes a comprehensive approach to pediatric endocrinology—looking beyond an isolated laboratory result to understand how a child’s **growth, development, nutrition, puberty and physiology fit together.** --- # References **1.** *Laboratory-Based Case Finding Using Phosphate and Alkaline Phosphatase.* **Frontiers in Endocrinology.** Published September 28, 2026. [Laboratory-Based Case Finding Using Phosphate and Alkaline Phosphatase](https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2026.1899612/full?utm_source=chatgpt.com) **2.** *Alkaline phosphatase levels in healthy children and evaluation of alkaline phosphatase z-scores in different types of rickets.* [Read the study on PubMed Central](https://pmc.ncbi.nlm.nih.gov/articles/PMC3065317/?utm_source=chatgpt.com) **3.** *Alkaline phosphatase in clinical practice in childhood: Focus on rickets.* **Frontiers in Endocrinology.** 2023. [Read the article in Frontiers in Endocrinology](https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2023.1111445/full?utm_source=chatgpt.com) **4.** *Approach to Hypophosphatemic Rickets.* **The Journal of Clinical Endocrinology & Metabolism.** 2023;108(1):209–220. [Read the article in JCEM](https://academic.oup.com/jcem/article/108/1/209/6671527?utm_source=chatgpt.com) **5.** *Rickets guidance: Part I—diagnostic workup.* **Pediatric Nephrology.** 2022;37:2013–2036. [Read the clinical guidance on PubMed Central](https://pmc.ncbi.nlm.nih.gov/articles/PMC9307538/?utm_source=chatgpt.com) --- # Medical Disclaimer This article is provided for **educational and informational purposes only** and is not intended to provide medical advice, diagnosis or treatment. Laboratory results in children must be interpreted in the context of the child’s age, sex, growth, development, medical history, symptoms and other clinical findings. Reference ranges may also vary by laboratory and testing method. Do not start, stop or change medications, supplements or treatment based on this article. 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