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Side Effects of Tolbutamide (Orinase, Tol-Tab)


Side Effects of Tolbutamide (Tol-Tab)

Tolbutamide, available as the brand Tol-Tab, is an antidiabetic prescription medicine part of the sulfonylurea class. Tol-Tab works by stimulating the release of natural insulin from the pancreas by lowering blood glucose levels. It is used for treating type II diabetes in patients who are unable to control their blood sugar levels by diet and exercise alone. It may be used alone or in combination with other antidiabetic medicines.

Before Taking Tol-Tab

The FDA advises to Inform your healthcare provider if you have the following medical conditions before beginning to use Tol-Tab: severe reaction in the past to any sulfonamide medicine, have a history of liver, kidney, thyroid, heart problems, drink alcohol, have or had poor nutrition, have type I diabetes, have a history of certain hormonal (endocrine) problems such as adrenal or pituitary problems.

Serious Side Effects

Intake of sulfonylurea-type antidiabetics, including Tol-Tab, has been associated with a higher risk of cardiovascular death, in comparison to treatment with diet alone or diet plus insulin.


Tol-Tab may cause low blood sugar levels. Low blood sugar may make you experience anxiety, sudden sweating, dizziness, fast heartbeat, blurred vision, shaking, hunger, or tingling hands/feet. Seek medical help if this occurs. To prevent low blood sugar, have a routine meal schedule and do not skip meals. There is an increased risk of low blood sugar by prolonged exercise, consuming alcohol, or skipping meals.


Other serious side effects of Tol-Tab include:


  • Jaundice (yellowing of the skin or eyes)
  • Light-colored stools
  • Dark urine
  • Pain in the upper right part of the stomach
  • Abnormal bruising or bleeding
  • Diarrhea
  • Fever
  • Sore throat


(Tol-Tab label reported by the FDA).

Common Side Effects

The FDA also lists the common side effects of Tol-Tab:


  • Upset stomach/a fullness feeling
  • Nausea
  • Headache
  • Weight gain

Drug Interactions

In individuals who have deficiency of the enzyme, glucose 6-phosphate dehydrogenase (G6PD), intake of sulfonylurea medicines like Tol-Tabe can cause hemolytic anemia (fast breakdown of red blood cells).

About Pharmacogenetic Testing

Tolbutamide is metabolized by CYP2C9, an enzyme activity of which could vary in different individuals due to genetic differences. Individuals with low activity of CYP2C9 are at risk of experiencing side effects.

Know Your Risk for Side Effects with the Rxight® Genetic Test

Many people are afraid of taking prescriptions due to adverse reactions and rising costs. One way to alleviate this problem is through the Rxight test. Rxight® can potentially enable healthcare providers to optimize Tol-Tab therapy. Rxight® also analyzes your reaction to hundreds of other common medications in addition to Tol-Tab, providing you with a “medication blueprint” for life.


The genetic test procedure involves a cotton swab to collect sample cells from inside the surface of the cheek. Once this is completed, the physician can see how the medication interacts with you and inform you on how you will handle the drug. You then have more understanding of the medicine and can make an informed decision about your prescription usage.


To receive more information on Rxight,® contact us at 1-888-888-1932 or at support@Rxight.com.


Contributors to this Article:
Michael Sapko, MD, PhD; and Deborah Kallick, PhD, Medicinal Chemistry

Read more about Rxight® : What is Pharmacogenetics?