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Phosphate (Phosphorus) Blood Test + Low Levels

Written by Biljana Novkovic, PhD | Last updated:
Jonathan Ritter
Puya Yazdi
Medically reviewed by
Jonathan Ritter, PharmD, PhD (Pharmacology), Puya Yazdi, MD | Written by Biljana Novkovic, PhD | Last updated:

Phosphorus is the second most abundant mineral in the body, essential for energy, bone, heart, lung, and brain health. Learn more about phosphorus, the cause and effects of low blood levels, and ways to increase them.

What is Phosphorus?

Phosphorus is the sixth most abundant element in the body after oxygen, hydrogen, carbon, nitrogen, and calcium. It is the second most abundant mineral and makes up about 1% of our body weight [1, 2].

Phosphorus is mainly found as phosphate in the body. The terms phosphate and phosphorus are often used interchangeably, although they don’t have the same meaning [2, 3]. Phosphorus is an atom, while phosphate is made when phosphorus is bound to oxygen (4 oxygen atoms).

85% of phosphorus in the body is stored in the bones. The remaining 15% is scattered in tissues throughout the body [4, 5].

Phosphorus has many important roles [2]:

  • Helps build cells, DNA, and proteins
  • Crucial for strong bones and teeth
  • Vital for energy metabolism, as the “P” of ATP – the “energy currency” of our cells
  • Required for muscle contractions and sending out nerve signals
  • As the most abundant anion (negative ion) in the body, phosphate helps maintain the acid-base balance (pH)

Blood phosphate comprises a very small part of total body phosphate. Nevertheless, it gives a good estimate of phosphate levels in the body [6].


Phosphorus is absorbed in the gut, stored in the bones, and removed by the kidneys.

Phosphate in the bones acts as a buffer that responds to specific imbalances. It moves in and out of bones as needed. Bone breakdown releases phosphorus, raising its blood levels. Increased bone mineralization, on the other hand, attracts phosphorus into the bones and lowers its blood levels [7, 2].

In adults, kidneys will normally get rid of a fairly constant amount of phosphorus (> 90%). But when the supply is low, kidneys can reabsorb phosphate very efficiently, reducing urine levels down to virtually zero. Also, when there’s phosphate overload, healthy kidneys can rid the body of any excess amounts [1, 2].

Apart from the obvious – gut, bones, and kidneys – blood phosphate levels are also controlled by the parathyroid gland. Hormones that affect blood phosphate levels are [2, 1, 8, 9]:

  • Calcitriol, or active vitamin D: promotes phosphorus absorption in the gut and increases blood phosphate levels
  • Parathyroid hormone: increases kidney excretion of phosphate and lowers blood phosphate levels
  • FGF23: increases kidney excretion of phosphate and decreases its gut absorption, reducing blood levels

Other hormones, such as thyroid hormones, insulin, corticosteroids, and calcitonin, have a more modest role in phosphate metabolism [1].

Phosphorus metabolism is tightly bound to that of calcium – both minerals are affected by the same hormones, usually in the opposite direction. In addition, phosphate can bind calcium in the blood, thereby reducing its levels. Our health depends on a delicate balance between these two minerals [2, 3].

Normal Range

You can measure your phosphate levels by doing a simple blood test.

Newborns have the highest phosphate levels (4.0 – 8.0 mg/dL) as they require more of this mineral for bone growth and soft tissue development. Levels in children are around 3.0 – 6.0 mg/dL and continue to gradually drop toward adulthood [2].

Accordingly, phosphate absorption and reabsorption (in the gut and kidneys, respectively) decline with age [2].

In adults, the normal range is between 2.5 and 4.5 mg/dL (milligrams per deciliter). That equals roughly 0.8 – 1.45 mmol/L (millimoles per liter).

Apart from age, phosphate levels are also influenced by [8, 10]:

  • Diet
  • Time of the day – levels are lowest in the morning and highest in the evening
  • Season – higher in the summer than winter
  • Gender – male children and adolescents have slightly higher levels
  • Genetics – some genetic mutations affect phosphate absorption in the gut and reabsorption in the kidneys

Low Phosphorus (Hypophosphatemia)

Low phosphate levels in the blood are called hypophosphatemia (“hypo” = low, “phosphatemia” = blood phosphorus). You may have low phosphate levels without noticing because symptoms and signs do not appear until the deficiency becomes serious.

However, a result that’s lower than normal, doesn’t necessarily mean that you have a health condition needing treatment. Your doctor will interpret your phosphate result, taking into account your medical history, symptoms, and other test results.


There are 3 main mechanisms that decrease phosphate levels [7]:

  • (1) inadequate phosphate intake and/or absorption
  • (2) increased kidney excretion
  • (3) increased cell and tissue needs

Phosphate deficiency is linked to various conditions, some of which only impact absorption, while others can affect more than one mechanism.

Causes shown below are commonly associated with low phosphate levels. Work with your doctor or another health care professional to get an accurate diagnosis.

Nutrition- or gut-related disorders

  • Long-term malnutrition and replenishment thereafter (the so-called “refeeding syndrome”), when phosphorus-depleted cells siphon all available free phosphate from the blood [7, 11]
  • Anorexia [12]
  • Potassium or vitamin D deficiency [6]
  • Poor absorption (malabsorption), in conditions such as Crohn’s disease [13, 7]
  • Chronic diarrhea, which also lowers gut phosphate absorption [13, 7]

Hormonal disorders

  • Hyperparathyroidism, or high parathyroid hormone levels, which leads to a greater loss of phosphate via kidneys [5, 7]
  • Hungry bone syndrome, which occurs after correcting hyperparathyroidism and results in an increased bone demand for phosphorus [7]
  • Hypothyroidism [14, 15]

Acid-base and/or metabolic disorders

  • Respiratory alkalosis, a condition that occurs when carbon dioxide levels drop too low due to hyperventilation or overbreathing (e.g. due to anxiety and panic attacks) [16, 7, 17, 18]
  • Gout [19]
  • Type 1 and poorly controlled type 2 diabetes. Glucose in the urine (glycosuria) increases phosphate loss through urine [7]

Other disorders

  • Alcoholism [20, 7]
  • Heat stroke, hyperthermia (abnormally high body temperature), or fever[21, 22, 23]
  • Severe burns [24, 25]
  • Severe infection (including sepsis, Legionnaires’ disease, and other respiratory infections) [26]
  • Kidney disease [27]
  • Tumor-induced softening of bones (oncogenic osteomalacia) [27]
  • Genetic disorders, such as X-linked hypophosphatemic rickets [7, 28]


Drugs that may decrease phosphate levels include [29, 7, 30, 31]:

  • Diuretics
  • Antacids
  • Bronchodilators and corticosteroids
  • Bisphosphonates, used to treat osteoporosis
  • Theophylline (used to treat asthma)
  • Insulin therapy
  • Intravenous iron

Symptoms and Signs

Most people with low phosphate levels are without symptoms. If you have mild hypophosphatemia, you may experience mild to moderate weakness in your body [7].

Generally, you will not experience symptoms unless your phosphate levels are very low (<1 mg/dL). In this case, you may experience [13, 27, 7]:

  • Loss of appetite
  • Anemia (due to hemolysis, or the destruction of red blood cells)
  • Muscle weakness
  • Irregular breathing
  • Burning or prickling sensation in various parts of the body (paresthesia)
  • Impaired coordination, balance, and speech (Ataxia)
  • Seizures
  • Confusion
  • Irregular heartbeat (arrhythmia)
  • Heart failure
  • Bone pain and fractures

Health Effects

1) Weakened Bones

Bones are continually being remodeled, undergoing a balanced breakdown and re-building (mineralization). In fact, most of the adult skeleton is completely replaced every 10 years or so [32].

Without sufficient phosphate, bone mineralization can come to a halt [2].

Long-term phosphate deficiency (hypophosphatemia) can lead to [7, 33, 34]:

  • Low bone mineral density (Osteopenia)
  • Brittle bones (Osteoporosis)
  • Softening of the bones (Osteomalacia)
  • Rickets, a disease that weakens the bones in children

2) Muscle Weakness

Low blood phosphate decreased ATP production, which is the main energy source in cells. Muscles need energy to effectively contract [35, 36].

Low phosphate can lead to muscle weakness, which can impact the heart muscle and the muscles needed for breathing.

3) Heart Disease

Studies have found that low phosphorus weakens the heart, reducing its blood-pumping power. It can also trigger an irregular heartbeat (arrhythmia) [37, 38].

In a large study of over 110,000 people, extreme blood phosphate levels – either too high or too low – increased the risk of heart disease (a so-called “U-shaped” relationship). But the deficiency does not need to be severe, even lower levels within the normal range may increase the risk [39].

4) Lung Function

Muscles of the diaphragm and rib cage allow us to breathe. Phosphate deficiency weakens these muscles and can lead to an inability to breathe (respiratory insufficiency). Although common in people with phosphate deficiency, this condition improves with phosphate repletion [40, 41].

5) Anemia

Although rare, low levels of phosphorus can rupture red blood cells, leading to anemia [42, 43].

6) Brain Health

Your nerves and brain cannot function well when phosphate is low. This can cause [44, 13, 40]:

  • A sensation of tingling and numbness (paresthesia)
  • Altered mental states
  • Irritability
  • Apathy
  • Delirium
  • Auditory and visual hallucinations
  • Paranoid delusions
  • Slurred speech
  • Seizures
  • Nerve pain

7) Metabolic Acidosis

Metabolic acidosis is a condition that occurs when the body produces excessive quantities of acid or when the kidneys are not removing enough acid from the body. Both scenarios can be triggered by low phosphate levels [45, 46].


Studies below suggest an association, but it’s impossible to discern cause and effect based on them.

8) Alzheimer’s Disease

In 109 people with mild cognitive impairment and 73 people with Alzheimer’s, those with lower blood phosphate levels had more beta-amyloid plaque buildup in the brain [47]. These plaques are the hallmark of Alzheimer’s disease.

In another study of 94 people, those with Alzheimer’s had lower blood phosphate than either the controls or patients with non-Alzheimer’s dementia [48].

9) Obesity

A study of over 46,000 people found a link between lower blood phosphate levels and higher BMI [49].

Lower phosphate levels were associated with obesity in both women and men in another study of almost 2,000 people [50].

Similarly, in a study of 298 children and adolescents, those who were obese had much lower blood phosphate levels [51].

10) Insulin Resistance

In 881 people, low blood phosphate was linked to greater spikes in blood glucose levels after sugar intake and poorer insulin sensitivity (ie. higher insulin resistance) [52].

Further, lower phosphate levels were associated with higher insulin resistance (HOMA-IR) in a study of 190 obese children and adolescents [51].

11) High Blood Pressure

In over 46,000 people, lower blood phosphate levels were linked with higher blood pressure (systolic and diastolic) [49].

In another study of 79 men, those with high blood pressure had lower phosphate levels than those who were healthy. What’s more, lower blood phosphate predicted higher blood pressure 20 years later in a study in 56 men [53, 54].

12) Metabolic Syndrome

Metabolic syndrome increases the risk of heart disease, stroke, and diabetes [55].

You have metabolic syndrome if you have any 3 of the following [56]:

  • High blood pressure
  • High blood sugar
  • Excess body fat around the waist
  • Low HDL cholesterol
  • High triglyceride levels

In over 46,000 people, lower blood phosphate levels were linked with lower HDL cholesterol and higher BMI, fasting glucose, insulin, insulin resistance (HOMA-IR), triglyceride levels, blood pressure, and waist circumference. People with low phosphate were also more likely to suffer from chronic inflammation, measured by hs-CRP [49].

In 56 men, those with the lowest phosphate levels at baseline had the highest number of risk factors associated with metabolic syndrome 20 years later [54].

13) Mortality

In over 42,000 hospitalized patients, blood phosphate levels in the extreme range (high or low) were associated with a greater risk of dying. Low phosphate levels increased the risk by 1.6 times [57].

In over 3,200 kidney disease patients on dialysis, low phosphate levels were associated with dying (from any cause or infection) [58].

Increasing Blood Phosphorus

The most important thing is to work with your doctor to find out what’s causing your low phosphate and to treat any underlying conditions!

In mild hypophosphatemia, your doctor may prescribe phosphate supplements. In severe and symptomatic cases, intravenous phosphate may be needed [7].

The additional lifestyle changes listed below are other things you may want to discuss with your doctor. None of these strategies should ever be done in place of what your doctor recommends or prescribes!

Make sure you are eating enough and that your diet is healthy and well balanced. Phosphate is found in lots of different foods. Good sources include dairy products, whole grains, meat, and fish [59].

Also, make sure your diet contains enough of all other important nutrients, such as potassium, vitamin D, and magnesium [6, 60, 61].

Quitting alcohol after chronic abuse can rapidly improve phosphate levels [62].

If your drugs lowering your phosphorus levels, discuss alternative options with your doctor [29].

If you suffer from anxiety, pay attention to your breathing. When you panic, you tend to breathe fast and shallow – in other words, you hyperventilate. This triggers a set of reactions in your body that decrease blood phosphate levels [63]. If you are prone to anxiety, engage in activities that promote deep and slow breathing, such as breathing exercises, meditation, or yoga.

If your drugs are causing lower phosphorus levels, discuss alternative options with your doctor [29].

About the Author

Biljana Novkovic

Biljana Novkovic

Biljana received her PhD from Hokkaido University.
Before joining SelfHacked, she was a research scientist with extensive field and laboratory experience. She spent 4 years reviewing the scientific literature on supplements, lab tests and other areas of health sciences. She is passionate about releasing the most accurate science and health information available on topics, and she's meticulous when writing and reviewing articles to make sure the science is sound. She believes that SelfHacked has the best science that is also layperson-friendly on the web.


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