Ask the doctors: Enlarged red blood cells can come from alcohol use

Dear Doctors: My husband is having an elective surgery soon. It requires full anesthesia, so he has had a lot of pre-op tests. One of the blood tests showed that his red blood cells are too big. The nurse said it happens when you drink too much. What causes that? Is it dangerous?

Dear Reader: When someone’s red blood cells become abnormally large, it is a condition known as macrocytosis. These enlarged blood cells are nutrient-poor and break down faster than normal cells. The name of the condition derives from Greek, with “macro” meaning large in scale, “cyto” referring to cells and “osis” indicating an abnormal condition.

Unless it is quite severe, macrocytosis usually does not cause any noticeable symptoms. As a result, it is often discovered in the course of routine blood tests, such as the pre-operative workups your husband was asked to undergo. Those workups typically include a test known as a complete blood count, or CBC. The size of someone’s red blood cells is one of the findings included in a CBC.

Macrocytosis isn’t a disease or disorder. Rather, it is a sign that an underlying health condition may be present. It is often linked to a deficiency of vitamin B12, which is absorbed from the blood and stored in the liver. B12 deficiency is common in people who abuse alcohol. Chronic alcohol abuse leads to widespread inflammation of the liver, and over time it will cause liver damage. That damage reduces the body’s ability to absorb, store and release B12, which in turn can result in macrocytosis.

Malabsorption of B12 can have other causes, as well. These include conditions such as Crohn’s disease or celiac disease, hemolytic anemia, bacterial overgrowth, bariatric surgery, certain cancers and intestinal parasites. The use of certain medications can also impair absorption of B12 and lead to a deficiency. These include proton pump inhibitors and H2 blockers, which are used to manage acid reflux; some chemotherapy drugs; and colchicine, which is used to treat gout. It is also possible to become deficient in vitamin B12 when following a vegan diet, which excludes food products made from and by animals. Because B12 is not produced by plants, vegans must be vigilant about using supplements and eating foods fortified with the vitamin to maintain adequate levels. Generally poor nutrition in any type of diet can lead to low folate levels, also a factor in macrocytosis.

If alcohol use is suspected as a cause of this condition, the person may be asked to undergo a liver function test. It can either pinpoint or rule out the liver as the source of the individual’s B12 deficiency. Other types of blood tests can identify whether the condition is linked to problems in blood cell development. A bone marrow biopsy can also reveal issues with red blood cell production.

If macrocytosis is linked to B12 deficiency, steps are taken to improve the individual’s diet and address any issues of malabsorption. And when alcohol abuse plays a role, a conversation about either moderation or abstinence is likely to take place.

Send your questions to askthedoctors@mednet.ucla.edu.