Diagnosing Vitamin B12 Deficiency: Urine Test
One of the most frequent methods of checking vitamin B12 levels in the body is by measuring the concentration of B12 in the blood serum. This value however is not actually very informative, as the test also measures vitamin B12 in the blood that is unavailable to the body. Unfortunately, a clinical vitamin B12 deficiency can still be present within the cells even when B12 levels appears to be normal in the blood. A more worthwhile test is therefore to measure either the bioavailable vitamin B12 (via a holo TC test) or the concentration of various metabolic products which change when there is a cellular B12 deficiency; namely the concentrations of homocysteine and methylmalonic acid (via an MMA test).
Methylmalonic Acid – A Clear Indication of Vitamin B12 Deficiency
When the body is vitamin B12 deficient, the concentration of methylmalonic acid (MMA) rises both in the blood and urine. Since there is only one B12 dependent metabolic pathway for the conversion of MMA, the methylmalonic acid urine test is a reliable indicator of a functional B12 deficiency. A distortion in results is only possible here with certain rare hereditary diseases, serious nutritional deficiencies and a rare bacterial overgrowth in the intestinal tract. As a result, the MMA urine test is seen as the most reliable method for determining vitamin B12 deficiency, alongside the the holo TC test.
Vitamin B12 Deficiency Urine Test: Method and Cost
The MMA urine test is very simple to perform; a sample of the morning urine is all that is required. This is then sent to a corresponding lab for testing. A self-examination, for example with a test strip, is unfortunately not possible. Depending on the company, the cost of an MMA test varies and unfortunately they can be quite expensive, unless prescribed by the doctor.
Possible Distortions of Test Results
It is very importance that the urine sample used in an MMA test is definitely the first morning urine, i.e. that no urine has been lost overnight. Here we asked a naturopath to comment on her experience of distorted results:
“My experience with contradictory values (serum B12 or holo TC vs MMA) has been frequently due to the fact that the urine sample was often not the first morning urine; patients had used the toilet throughout the night. As a result, the metabolism of the day before was not present in the sample […] For a meaningful test, I consider it essential that if patients struggle with producing a genuine morning sample, they collect samples every time they go to toilet after midnight, which can be mixed with the first morning urine and tested. This can be done without the need for expensive collection vessels, for example by using a new polyethylene freezer bag (the common sample cups are made of the same material, as it does not affect results). Since I have introduced these instructions to my patients, there have been practically no unexplainable contradictions in results”.
In addition, no supplements should be taken for 10 days before the test in order to prevent false results.
Analysis of Vitamin B12 Urine Test
Analysing the test is just as simple as taking it; the concentration of MMA is measured in relation to the concentration of creatine, to account for fluctuations in the excretion capacity of the kidneys.
up to 3.6 mmol MMA/mol creatine
up to 2 mg MMA/g creatine
No vitamin B12 deficiency
over 3.6 mmol MMA/mol creatine
over 2 mg MMA/g creatine
Vitamin B12 deficiency
Interpretation of Test Values and Treatment Guidelines
After test results have been received, the next question is how to interpret them and, of course, what to do next. Unfortunately, each laboratory has a different definition of deficiency and use various units of measurement. The values are usually given in mg of B12 per g of creatinine. Common limits are 2 mg/g creatinine and 2.6 mg/g creatinine. We are of the opinion that a deficiency can be expected even at a value of 2 mg/g, so subsequently this is the limit that we use. The following table shows a possible interpretation of the results of a urine test and gives suitable treatment guidelines.
|Clearly under the limit|
< 1.5 mg/g
Roughly around the limit
Low dosage supplement to defend against any minor symptoms
5-10 µg oral/day
|Clearly over the limit|
> 2.5 mg/g
|To begin taking supplements and to seek the cause of the deficiency|
250 – 500 µg oral/day
> 5 mg/g
To begin taking supplements and seek the cause of the deficiency.
Consult a therapist.
Consider taking a blood test for holo TC and homocysteine with a doctor, to verify the result.
|500 µg oral/day|
1000 µg/week injection for 4 weeks
Who Should Take a B12 Deficiency Test?
The elderly, vegetarians and vegans should check their vitamin B12 levels regularly, as these people are most likely to suffer from deficiency. Additionally, testing is highly recommended for anyone with several deficiency symptoms. In particular, patients with anaemia, dementia, multiple sclerosis, fibromyalgia and chronic fatigue should certainly check their B12 status, since deficiency may be worsening the symptoms here. Most doctors and naturopaths recommend first carrying out a test, before supplementation begins.
What to do if You are Vitamin B12 Deficient?
If test results reveal a B12 deficiency, it is highly recommended to start taking vitamin B12 supplements. At the same time, it is important to begin looking into the root cause of deficiency. If diet is not the cause, then there is probably malabsorption in the gastrointestinal tract, which should be further investigated. In the majority of cases, gastrointestinal tract diseases play a major role here.
For more information on this topic, see the article: Vitamin B12 Deficiency Causes
When taking supplements, it is important to obtain an ample dose in order to replenish the body’s store of vitamin B12, which is likely to be very low. After this initial period, a lower maintenance dose can be taken to cover the body’s daily requirement.
Further detailed information here can be found in the article: Vitamin B12 Dosages