Reasons, Preparation and Procedure To Test Arsenic Levels in Urine

Submitted on March 27, 2012

Arsenic is a highly toxic heavy metal that belongs to the same category as lead and mercury. While trace amounts of arsenic are common in the body, these are usually converted to harmless forms by detoxification, or are excreted in the urine. However, excess amounts of arsenic in the tissues, lead to severe medical problems, and can even lead to death. Such excess arsenic is usually detectable in keratin-rich tissues such as hair and nails.

Symptoms of arsenic poisoning include swelling of facial tissues, hair loss, abnormalities of the digestive system and urinary tract, changes in skin texture and color, and several types of cancer. While short-term, high level dosages are instantly toxic, most cases of long-term exposure are difficult to detect and diagnose, since the symptoms appear over years and can be mistaken for other diseases.


Until the introduction of the Marsh Test in 1836, it was impossible to confirm a case of arsenic poisoning, whether deliberate or accidental. Since then, arsenic tests have improved tremendously and can detect the minutest traces of arsenic in the human body. The urine arsenic level is often the preferred method, since it provides more accurate results. On the other hand, testing on hair and nail samples is useful in cases of low level, long term exposure. Arsenic levels in urine can also be differentiated between organic arsenic from the normal food chain and inorganic arsenic from other sources. This is important since most medical complications arise due to the inorganic types of arsenic.


In some cases, the patient may be asked to avoid shellfish for at least 3 days before the urine sample is collected. The urine samples may also be collected over a day or two to improve the accuracy of results. This helps to get a clear indication of the body's ability to metabolize the organic arsenic and detoxify any harmful inorganic arsenic. The doctor may also require a list of all the medications being taken by the patient, as well as any chronic medical conditions.


Once the urine sample is collected, there are several laboratory methods to test for levels of arsenic. Many of these can separate the various types of organic and inorganic arsenic by identifying certain metabolies such as methylarsonic acid (MMA) and dimethylarsenic acid (DMA). The final results are expressed purely in terms of the toxic inorganic arsenic. The normal levels in the arsenic urine test conducted over a 24-hour period should not be more than 50 mcg in healthy adults.