Iodine & Creatinine (I & CRTN) Test Kit

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The Iodine & Creatinine (I & CRTN) Urine Spot Test Kit is a specialised testing tool designed to measure the levels of iodine and creatinine in the human body accurately. It provides a convenient and reliable method for assessing these important substances in both males and females. The test is also suitable for children.

Iodine is an essential mineral that plays a crucial role in maintaining proper thyroid function and overall health. It is necessary for the production of thyroid hormones, which regulate metabolism, growth, and development. This kit's Iodine spot test component allows individuals to determine their iodine levels quickly and conveniently. By assessing iodine levels, one can gain insights into thyroid health and ensure one meets daily iodine requirements.

On the other hand, Creatinine is a waste product produced by the muscles during normal metabolism. It is primarily eliminated from the body through the kidneys. The Creatinine spot test in this kit allows individuals to assess the levels of creatinine in their urine. This information is valuable in evaluating kidney function, as abnormal creatinine levels may indicate potential kidney problems or conditions.

The I & CRTN Urine Spot Test Kit provides a user-friendly and non-invasive method for individuals to monitor their iodine and creatinine levels. The kit typically includes all the necessary components, such as testing strips or reagents, as well as clear instructions on how to perform the test accurately.

By using this test kit regularly, individuals can keep track of their iodine and creatinine levels over time, enabling them to make informed decisions about their diet, lifestyle, and overall well-being. It is important to note that while this test kit provides valuable insights, it should not be considered a substitute for professional medical advice. In case of any concerns or abnormal results, it is advisable to consult with a healthcare professional for further evaluation and guidance.

Iodine Deficiency

Iodine deficiency or excessive iodine levels can have a negative impact on your health, including the development of goitre, hypothyroidism, acneiform eruption, and reduced mental function. This dry urine test will also help determine the effectiveness of iodine supplementation in an individual and track treatment progress. It is easy to use and only requires urine collection on a filter strip two times a day.

Test result: This kit is safe, and it is easy to verify the level of iodine. Once the laboratory obtains and analyzes your sample (dried urine), you will receive the test result within 3-5 working days. In your test result, you will find the following:

  • Your Iodine and Creatinine values are in graphical form, making it possible to decipher whether the iodine levels are within the normal range.
  • Easy to understand explanation regarding the functions of the tested Iodine by our laboratory professional.
  • Tips and advice on what to do next.

We strongly recommend that you consult your results with your health care provider, GP, or doctor to know whether or not any further actions need to be carried out and get started with ample treatment if needed.

What is Iodine and what does it do for the human body?

Iodine is a mineral found in some foods. The body needs iodine to make thyroid hormones, which control the body's metabolism and other important functions. The body also needs thyroid hormones for proper bone and brain development during pregnancy and infancy.

Who needs iodine the most and how much do I need of it?

Getting enough iodine is important for everyone, but it is especially critical for infants and women who are pregnant. Each day depends on the person's age, how much iodine is needed. Average daily recommended amounts are listed below in micrograms (mcg).

Life Stage

Recommended Amount

 Birth to 6 months

110 mcg  

 Infants 7-12 months

130 mcg  

 Children 1-8 years

90 mcg  

 Children 9-13 years

120 mcg  

 Teens 14-18 years

150 mcg  


150 mcg  

 Pregnant teens and women

220 mcg  

 Breastfeeding teens and women

290 mcg  

Iodine deficiency is a global health problem

Approximately 2 billion of the world’s population is iodine deficient. According to the most recent NHANES surveys3,4, urinary iodine levels have dropped in the U.S. by half since the 1970s, and nearly 10% of the population has some degree of iodine deficiency. Iodine deficiency is resurfacing in developed countries like the U.S. and Western Europe as efforts are made to reduce the consumption of iodine-containing salt and foods (eggs and dairy) to lower blood pressure and blood lipids. 

Adequate Iodine is Essential at All Stages of Life

In the developing fetus, and adequate iodine supply from the mother is essential for thyroid hormone production, which is vital for proper neurological development. In those areas of the world with severe iodine deficiency, pregnant women are at increased risk of miscarriage, stillbirths, or giving birth to children with cretinism and severe neurological and developmental defects. Even in areas of the world with mild to moderate iodine deficiency, which includes some regions of the U.S.children born to mothers who are iodine deficient during pregnancy can have impaired intellectual development and are at increased risk for developing attention deficit and hyperactivity disorders. 

In children and adults, iodine deficiency can lead to lower thyroid hormone synthesis and consequent symptoms and conditions of hypothyroidism1,2. When iodine levels drop below a critical threshold, consequent low thyroid hormone levels signal the brain to increase TSH production. Excessive stimulation of the thyroid gland by TSH, caused by iodine deficiency, leads to overgrowth (goitre) in an effort to maintain steady-state thyroid hormone synthesis. Areas of the world with low iodine usually have a much higher incidence of goitre.

Why high Iodine levels can be problematic:

High iodine levels, resulting from consumption of high iodine-containing foods (e.g., seaweed) or iodine medications or supplements, can also disrupt normal thyroid function, causing goitre and both hyperthyroidism or hypothyroidism. 

Hyperthyroidism is more likely to occur in the elderly who have been exposed acutely to high iodine after living for years in a low iodine environment. Chronic low iodine can lead to the development of autonomous thyroid nodules that produce excessive amounts of thyroid hormones (hyperthyroidism) when acutely exposed to high levels of iodine. Although rare, hyperthyroidism and associated thyrotoxicosis caused by excessive iodine consumption can cause arrhythmias and precipitate adverse cardiovascular events.

In some people, acute high iodine exposure can paradoxically suppress thyroid hormone synthesis (Wolff-Chaikoff effect) and lead to goitre and hypothyroidism13. The formation of iodolipids within the thyroid gland following high iodine exposure and their inhibition of TSH-activated thyroid hormone synthesis is thought to underlie the Wolff-Chaikoff effect. Ultimately, this results in the lower synthesis of T4 and T3 and a consequent increase in TSH. Most people with normal thyroid glands escape from the Wolff-Chaikoff effect within about two days. However a small percentage of people, particularly those with underlying subclinical hypothyroidism (normal T4 and T3, but elevated TSH) or with thyroid glands compromised by autoimmune problems (e.g., Hashimoto’s), are less likely to recover from the suppressive effects of high iodine, and progress to a more severe and permanent hypothyroid state that requires thyroid medication.

How does Iodine help prevent Infection:

Iodine’s effectiveness as an antimicrobial has been known for over a hundred years as it has been used for preoperative surgical skin preparation to prevent infection. As an antimicrobial, it is of relevance that iodine from the bloodstream concentrates in a broad spectrum of tissues that are repeatedly exposed to infectious organisms (e.g., skin, eyes, gastrointestinal tract, salivary gland, nasal and oral mucosa, breast ducts, uterine lining, prostate). Uptake of iodide by these tissues and enzymatic formation of reactive iodine compounds (e.g., hypoiodous acid) would serve the role of a protective antimicrobial, working in concert with the immune system. It is also of interest that like the thyroid, many of these iodine concentrating tissues (e.g., skin, eyes, gastrointestinal tract) are the most sensitive to the adverse effects of iodine excess. 

Iodine sufficiency is likely different in the Thyroid gland than in other tissues

Controversy exists as to how much iodine consumption is optimal. Sufficiency for the thyroid (about 150-300 µg daily consumption of iodine)2,15 is likely much lower than sufficiency for other tissues that are known to concentrate iodine such as the breast16,24,26,27,29. Studies in humans have shown that for iodine to be protective (prevent benign breast disease such as fibrocystic), a minimum of 3,000 µg and optimally 6,000 µg or more of daily iodine consumption are required24,27,28,29, far exceeding the CDC and WHO recommendations of 150-300 µg daily consumption of iodine-containing foods, salts, or supplements. The higher iodine levels found to be breast-protective are more consistent with the amounts of iodine consumed in countries like Japan, where the breast cancer rate is only about one-fifth that of the U.S. and other countries with much lower iodine consumption.

Development of a patient-convenient test to measure Iodine levels in dried urine

With iodine playing so many different roles in optimising health and preventing disease in the thyroid and other tissues, it is essential that adequate iodine intake is maintained and problems associated with low or excessive iodine intake are identified and treated appropriately.  To this end, ZRT has developed a simple and convenient test to measure an individual’s iodine level in urine dried on a filter strip. This method was developed to circumvent the more cumbersome collection of all urine over a 24 hour period.

Collecting and testing urinary Iodine

Iodine is collected twice during the day (first morning and last night void) on filter strips either by dipping the strip in urine collected in a cup, or by urinating directly on the strip. The urine-saturated filter strips are allowed to dry overnight and then sent to the laboratory for iodine and creatinine testing. The iodine content of the dried filter strips is determined following extraction and measurement by inductively coupled plasma mass spectrometry (ICP-MS). Creatinine is measured in the same urine extract by a modification of the Jaffe method33. Iodine is measured in µg per litre of urine, and the average of morning and night levels is taken. The creatinine level is used to correct for hydration status of the individual because it is dependent on urine dilution. Results are therefore expressed in µg of iodine per g of creatinine.

Assay validation

Iodine levels determined in extracts of urine dried on filter paper are quantitatively equivalent to measurements in wet urine (r2=0.99). Moreover, in individuals not supplementing with iodine, or eating iodine-rich foods, the average iodine level from the first morning and last night voids is equivalent to 24 hr collections, making the urine collection procedure much more patient convenient. ZRT Laboratory participates in the CDC-sponsored EQUIP (Ensuring the Quality of Iodine Procedures) iodine standardisation program where multiple urine samples are tested for iodine content and compared with values generated by ICP-MS at CDC and other laboratories performing iodine testing around the world (results available on request). 

Advantages of dried urine for Iodine & Creatinine (I&CRTN) testing:

• Urine collection and shipment of the dried filter strips are simple and convenient for the patient and practitioner.

• Dual collections of urine directly on a filter strip, upon awakening and just before bed, are far more convenient and less subject to the inherent inaccuracies of a 24 hr urine collection. 
• Iodine and creatinine in dried urine are exceptionally stable for weeks at room temperature, allowing more flexibility in the collection, shipment, testing, and storage.
• Iodine results expressed in µg iodine per g creatinine helps to normalise results when problems exist with urine that is very concentrated or dilute.
• Iodine testing allows for the determination of iodine status based on CDC and WHO guidelines for thyroid sufficiency, as well as extra-thyroidal sufficiency.