How Many Patients Are in Need of Vitamin B12 Injections?

• Change in plasma cobalamins [ Time Frame: Every month ] [ Designated as safety issue: Yes ]
• Change in plasma methylmalonic acid [ Time Frame: Every month ] [ Designated as safety issue: Yes ]
• Change in plasma holotranscobalamin [ Time Frame: Every month ] [ Designated as safety issue: Yes ]

• Change in plasma cobalamins
• Change in plasma methylmalonic acid
• Change in plasma holotranscobalamin

The clinical consequences of vitamin B12 deficiency include megaloblastic anemia and neurological disorders. Therefore, a proper and timely diagnosis and treatment is important. The use of sensitive biochemical markers such as methylmalonic acid for the diagnosis of vitamin B12 deficiency have increased since the 1980s. Consequently, the number of individuals treated with vitamin B12 has increased significantly.

The objective of this project is to study the actual need for vitamin B12 injections in the group of individuals who have already started treatment. In order to investigate this, the investigators stop vitamin B12 treatment in this group, and look for signs of vitamin B12 deficiency by monitoring changes in biochemical and hematological markers. Furthermore, they will test if the individuals are able to absorb a physiological dose of vitamin B12 using a recently developed absorption test (CobaSorb). If a physiological dose can be absorbed, the vitamin B12 injections can be replaced with tablets. In the end, the investigators hope to be able to divide the patients into three groups:

1. need life long injections with vitamin B12,
2. only need supplementations with a small dose of oral vitamin B12, and
3. no need for further vitamin B12 treatment.

The perspective is that the new information from this study might be used for a future strategy for vitamin B12 treatment.

The clinical consequences of vitamin B12 deficiency include megaloblastic anemia and neurological disorders. Therefore, a proper and timely diagnosis and treatment is important. The use of sensitive biochemical markers such as methylmalonic acid for the diagnosis of vitamin B12 deficiency have increased since the 1980s. Consequently, the number of individuals treated with vitamin B12 has increased significantly.

The objective of this project is to study the actual need for vitamin B12 injections in the group of individuals who have already started treatment. In order to investigate this, the investigators stop vitamin B12 treatment in this group, and look for signs of vitamin B12 deficiency by monitoring changes in biochemical and hematological markers. Furthermore, they will test if the individuals are able to absorb a physiological dose of vitamin B12 using a recently developed absorption test (CobaSorb). If a physiological dose can be absorbed, the vitamin B12 injections can be replaced with tablets. In the end, the investigators hope to be able to divide the patients into three groups:

1. need life long injections with vitamin B12,
2. only need supplementations with a small dose of oral vitamin B12, and
3. no need for further vitamin B12 treatment.

The perspective is that the new information from this study might be used for a future strategy for vitamin B12 treatment.

Inclusion Criteria:

• Above 17 years old
• Have received vitamin B12 treatment for at least one year
• Capable of reading and understanding Danish

Exclusion Criteria:

• Pregnant or nursing women
• Not capable of giving informed consent
• Acute infection during the 3-day examination of vitamin B12 absorption