A severe B12 deficiency results in anemia, which can be picked up by an ordinary blood test. But the less dramatic symptoms of a B12 deficiency may include muscle weakness, fatigue, shakiness, unsteady gait, incontinence, low blood pressure, depression and other mood disorders, and cognitive problems like poor memory.
http://www.nytimes.com/2011/11/29/health/vitamin-b12-deficiency-can-cause-symptoms-that-mimic-aging.html
Anaemia and anaemia caused by a lack of vitamin B12 can result in symptoms which include: 1  Extreme tiredness or fatigue. 2  A lack of energy or lethargy. 3  Being out of breath. 4  Feeling faint. 5  Headache. 6  Ringing in the ears (tinnitus).
http://www.webmd.boots.com/healthy-eating/guide/vitamin-b12-deficiency
Anaemia and anaemia caused by a lack of vitamin B12 can result in symptoms which include: 1  Extreme tiredness or fatigue. 2  A lack of energy or lethargy. 3  Being out of breath. 4  Feeling faint. 5  Headache. 6  Ringing in the ears (tinnitus). 7  Lack of appetite.
http://www.webmd.boots.com/healthy-eating/guide/vitamin-b12-deficiency
But the less dramatic symptoms of a B12 deficiency may include muscle weakness, fatigue, shakiness, unsteady gait, incontinence, low blood pressure, depression and other mood disorders, and cognitive problems like poor memory.
http://www.nytimes.com/2011/11/29/health/vitamin-b12-deficiency-can-cause-symptoms-that-mimic-aging.html
Vitamin B12 deficiency symptoms. Low vitamin B12 symptoms can be in the form of muscle weakness, skin tingling, numbness, sleeping problems (inability to sleep) anxiety, poor balance, tiredness and more colds in a year.
http://www.myhealthyfeeling.com/low-vitamin-b12-causes-symptoms-treatment/
Symptoms of vitamin B12 deficiency. Anaemia and anaemia caused by a lack of vitamin B12 can result in symptoms which include: 1  Extreme tiredness or fatigue. 2  A lack of energy or lethargy.
http://www.webmd.boots.com/healthy-eating/guide/vitamin-b12-deficiency
Having vitamin B12 deficiency means that your body does not have enough of this vitamin. You need B12 to make red blood cells, which carry oxygen through your body. Not having enough B12 can lead to anemia, which means your body does not have enough red blood cells to do the job. This can make you feel weak and tired.
http://www.webmd.com/a-to-z-guides/vitamin-b12-deficiency-anemia-topic-overview
General symptoms of anaemia (where you have fewer red blood cells than normal or you have an abnormally low amount of a substance called haemoglobin in each red blood cell) include: 1  extreme tiredness (fatigue). 2  lack of energy (lethargy). 3  breathlessness. 4  feeling faint. 5  headaches.
http://www.nhs.uk/Conditions/Anaemia-vitamin-B12-and-folate-deficiency/Pages/Symptoms.aspx
Some people diagnosed with Alzheimer's disease have been found to have abnormally low vitamin B12 levels in their blood. The effects of vitamin B12 supplementation on the prevention or progression of Alzheimer's disease remain unclear. More studies are needed before a conclusion can be made.
http://www.mayoclinic.org/drugs-supplements/vitamin-b12/evidence/HRB-20060243
B12 deficiency anemia may also be caused by a lack of intrinsic factor-pernicious anemia. The patient's digestive system cannot absorb B12 properly. Signs and symptoms of pernicious anemia may include: 1  Fatigue. 2  Shortness of breath. 3  Palpitations.
http://www.medicalnewstoday.com/articles/172774.php
symptoms of low b12 in men
Weakness, fatigue, shakiness, unsteady gait, incontinence, low blood pressure, depression and other mood disorders, and cognitive problems like poor memory are the symptoms of low B12 in men. Weakness, fatigue, shakiness, unsteady gait, incontinence, low blood pressure, depression and other mood disorders, and cognitive problems like poor memory are the symptoms of low Vitamin B12 in men.