维生素B12是您的身体对过程所需的重要营养素，例如DNA合成，能量产生和中枢神经系统功能（ 1 ).

即使在许多食物中发现了维生素，B12的不足和缺乏症相对普遍。这通常是由于饮食摄入量有限，吸收不良，某些医疗状况或使用B12的药物（ 2 , 3 , 4 ).

In fact, studies suggest that up to 20% of people over the age of 60 in the United States and the United Kingdom are deficient in the vitamin ( 5 ).

For reference, B12 levels above 300 pg/mL are considered normal, levels of 200–300 pg/mL are considered borderline, and levels below 200 pg/mL are considered deficient ( 2 ).

由于能够随着年龄的增长而从食物下降中吸收B12的能力，因此缺乏症在老年人中更为常见。尽管如此，这并不意味着儿童和年轻人，包括怀孕和母乳喂养的儿童和年轻人，无法造成B12缺乏症（ 5 , 6 ).

Unfortunately, B12 deficiency is often overlooked and misdiagnosed. Oftentimes, this is due to inadequate laboratory testing or because the symptoms are not specific to vitamin B12 deficiency alone ( 7 ).

如果您怀疑自己可能缺乏B12，那么访问医疗保健专业人员以讨论您的症状并进行适当的测试很重要。

本文涵盖了与B12缺乏症有关的最常见症状以及如何诊断和治疗这种缺乏症的症状。

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If you’re low or deficient in B12, you’ll likely feel fatigued.

Your body’s cells need B12 to function properly. As such, having inadequate B12 levels can decrease normal red blood cell production, which can impair oxygen delivery ( 8 ).

Specifically, a deficiency in B12 or folate can causemegaloblastic anemia. This condition leads to the formation of large, abnormal, and immature red blood cells and impaired DNA synthesis ( 2 , 9 ).

当您的身体没有足够健康的红细胞将氧气带到组织中时，您可能会感到虚弱和疲倦。

重要的是要知道，即使您的B12水平被视为范围内或仅在范围内，也可以发展与B12缺乏症有关的疲劳和其他症状（ 6 ).

可能表明B12缺乏症的另一个迹象是苍白或黄色的皮肤。

Like the condition called缺铁性贫血, anemia related to B12 deficiency may make your skin pale due to a lack of fully-matured, healthy red blood cells in the body ( 2 ).

B12 deficiency can also cause a condition called jaundice, which makes your skin and the whites of your eyes take on a yellowish color.

The color is caused by high levels of bilirubin, a waste product created when your body breaks down red blood cells ( 2 ).

B12不足和缺乏会导致神经系统副作用，包括头痛。

In fact, headaches are amongst the most commonly reported symptoms related to B12 deficiency in both adults and kids ( 2 , 10 , 11 ).

Some studies have shown that people who frequently experience certain types of headaches are more likely to have low B12 levels.

2019年的一项研究，有140人，其中一半的经历migraines, found that blood levels of B12 were significantly lower in the participants with migraines compared with the participants with no migraine history ( 12 ).

The study also found that those with the highest B12 levels were 80% less likely to have migraines compared with participants with the lowest B12 levels ( 12 ).

Research continues to investigate if treatment with B12 may improve migraine headache symptoms in some people ( 13 ).

B12 is essential to the proper functioning of your central nervous system, and a deficiency in this nutrient can impact your mental health.

Specifically, B12 deficiency is associated with a greater risk of developing depression ( 14 , 15 ).

Having low levels of B12 can cause elevated levels of a sulfur-containing amino acid calledhomocysteine. In turn, this may contribute to the development of depression by increasing oxidative stress, DNA damage, and cell death in the body ( 16 , 17 ).

2020年的一项研究有132儿童和青少年,89和43 without depression, found that the participants with depression had lower B12 levels and higher levels of homocysteine compared with those without depression ( 17 ).

In addition to depressive symptoms, low or deficient B12 levels may lead to other mental conditions, including psychosis and mood disorders ( 18 ).

A B12 deficiency may also cause diarrhea, nausea, constipation,bloating，气体和其他胃肠道症状（ 2 , 19 ).

These issues can affect both adults and children ( 2 , 20 ).

Keep in mind, though, that many of these symptoms are non-specific and could be caused by other factors. For example, food intolerances, medications, and infections could all lead to diarrhea.

Because a deficiency in B12 negatively impacts the central nervous system, people with low or deficient B12 levels may feel foggy-headed and have difficulty concentrating and completing tasks ( 21 ).

Older adults are especially at risk for these side effects because the risk of B12 deficiency increases with age.

In fact, many studies have associated low B12 levels with worsened mental function in older adults ( 22 , 23 ).

Fortunately, studies show that mental impairment related to low B12 levels can improve with B12 treatment.

例如，一项2020年的研究使202人患有轻度精神障碍，低正常或低正常的B12水平，同型半胱氨酸水平升高B12替代疗法3个月（ 21 ).

治疗后，有84％的参与者报告了症状的显着改善，例如焦点不良，memory decline, and forgetfulness ( 21 ).

Glossitis is a medical term that refers to an inflamed, red, and painful tongue. It can be caused by a B12 deficiency ( 24 ).

在这种缺乏症的人中词汇炎can appear alongside stomatitis, which is characterized by sores and inflammation in the mouth ( 25 ).

Even though glossitis and stomatitis are common in people with B12 deficiency-related anemia, they can also occur without anemia and can be a sign of an early B12 deficiency ( 25 ).

话虽这么说，词汇炎也可能是由于其他营养素（例如叶酸，核黄素（B2）和烟酸（B3）（B3）（B3）（B3）（B3）（B3）的缺乏症引起的 25 ).

Paresthesiais a medical term that refers to a burning or pins-and-needles sensation in certain areas of the body, like the hands and feet.

许多患有B12缺乏症报告的成年人和儿童经历了感觉异常（ 7 , 20 ).

Unfortunately, this symptom of B12 deficiency overlaps with symptoms related to diabetic neuropathy — nerve damage caused by high blood sugar that can cause pain and numbness in the extremities ( 26 ).

服用二甲双胍的糖尿病患者患B12缺乏症的风险更高，因为这种药物可以减少体内维生素B12的吸收（ 4 ).

So, a B12 deficiency could be misdiagnosed as peripheral neuropathy in people with diabetes.

As a result, many experts recommend that people taking metformin regularly get screened for vitamin B12 deficiency.

In addition to the symptoms above, B12 deficiency may lead to the following:

  • 肌肉痉挛和肌肉无力。B12 deficiency negatively impacts motor and sensory nerve function, which can cause muscle cramps and weakness ( 7 , 27 ).
  • Impaired coordination.Ataxia, or impaired balance and coordination, is a neurological symptom that can be caused by B12 deficiency. As such, a person with B12 deficiency may have difficulty walking and balancing ( 2 ).
  • Erectile dysfunction.Men with B12 deficiency may experience erectile dysfunction as a result of increased levels of homocysteine in the body ( 28 ).
  • 视力干扰。B12 deficiency may cause vision disturbances, possibly due to damage to the optic nerve ( 29 )

Because vitamin B12 deficiency symptoms aren’t specific to the condition, it may go undetected or get misdiagnosed.

If you’re experiencing any of the symptoms listed above, it’s important to discuss them with a healthcare professional.

This is especially relevant if you:

  • follow a restrictive diet, likea vegan diet
  • 超过60岁
  • are pregnant or breastfeeding
  • 具有可以耗尽B12水平的疾病
  • take a B12-depleting medication, like metformin or proton pump inhibitors

除了学习症状并给您身体检查外，医疗保健专业人员还可以通过订购血液检查来排除B12缺乏症。

These tests can include ( 2 ):

  • B12 levels
  • 叶酸水平
  • a complete blood count (CBC) with a peripheral smear
  • methylmalonic acid (MMA) levels
  • homocysteine levels

If you’re diagnosed with too low B12 levels, your healthcare professional will recommend the most appropriate treatment. It may include B12 injections, oral B12 supplements, or addressing an underlying health condition that could be causing the deficiency ( 2 ).

B12 injections are generally recommended for people who can’t properly absorb B12 from food or supplements, like those who’ve undergone gastric bypass surgery or people with certain autoimmune diseases ( 2 ).

B12补充剂和注射是安全的和well-tolerated, even in large doses ( 1 ).

概括

如果您的医疗保健专业人员认为您在B12中可能很低，他们将订购适当的血液检查以评估您的B12水平。B12缺乏症的治疗通常包括口服补充剂或注射。

B12 deficiency can cause a variety of symptoms, including fatigue, headaches, depression, pale or yellow skin, mental impairment, and pain and inflammation in the mouth and tongue.

低B12水平引起的许多症状不是B12缺乏症的特异性，这可能导致该病未被发现。

If you’re experiencing any of the symptoms listed above, it’s important to visit a healthcare professional to undergo appropriate testing and get the right treatment.