low sugar

What blood sugar is too low?

Many people are confused about what low blood sugar actually means. 

Some people think they are having dangerously low blood sugar when they are not. This can lead to unnecessary anxiety, over treatment, overeating and weight gain.

On the other hand, many people with diabetes think having dangerously low blood sugar is better than having high sugar. This is also not true. Low sugar can be acutely dangerous because it can lead to loss of consciousness and even death quickly if not correctly. 

In patients with diabetes who are treated with hypoglycemic agents, medications that can cause dangerously low blood sugars, we want to prevent low blood sugar. These medications include insulin and sulfonylureas such as glipizide, glimepiride and glyburide. When a patient on these medications regularly has blood sugar less than 100mg/dL, we should reduce their medication dose. A patient taking these medications should correct a low blood sugar by ingesting carbohydrate or with glucagon if not conscious if their blood sugar drops lower than 70mg/dl.

Most other medications  for diabetes do not cause dangerously low blood sugar. 

If not on hypoglycemic medications for diabetes, can blood sugar be too low? 

In these cases, a person must meet all three criteria of Whipple’s Triad for hypoglycemia to meet criteria for further workup of hypoglycemia.

Whipple’s Triad consists of:

  1. Low blood sugar on serum (or finger stick since finger stick is much more practical). It is important to note that continuous glucose monitoring systems (CGMS) are inaccurate when low so you must check a fingerstick capillary blood glucose if using CGMS to confirm a low blood sugar.
  2. Symptoms of low sugar (sweating, anxiety, tunnel vision, hunger, agitation)
  3. Symptoms must improve with ingesting carbohydrates

If all criteria of Whipple’s Triad are not met in a person who is not taking hypoglycemic agents, they do not meet diagnostic criteria for hypoglycemia. Thus, further workup of hypoglycemia is not warranted. Their symptoms and concerns are important, though, so they should be addressed.

Non-diabetic hypoglycemia is exceedingly rare. Bariatric surgery increases risk for hypoglycemia syndromes such as nesidioblastosis and dumping syndrome. Rare conditions that cause low blood sugar are insulin-secreting tumors called insulinomas and some types of cancer. Some healthy people have transient post-meal hypoglycemia that typically occurs after ingestion of a high carb meal. This post-meal hypoglycemia typically improves with eating meals with lower carb load.

Watch Dr. Thangudu’s video on hypoglycemia to learn more!