An A1C test, also called a glycated hemoglobin test, is a blood test that provides information about your average levels of blood glucose over the past 3 months. The A1C is used to diagnose type 1 and type 2 diabetes and to keep track of how well diabetes is being managed.
Some medications can increase blood glucose levels and therefore increase A1C values. Being aware of these medications is important for people with diabetes so they can work with their healthcare provider to make adjustments to their treatment plan if needed.
How A1C relates to blood glucose
The A1C test measures the amount of glycated hemoglobin in the blood. Hemoglobin is the protein in red blood cells that carries oxygen. Glycation is when glucose attaches to hemoglobin.
The more glucose in the blood, the more hemoglobin gets glycated. By measuring glycated hemoglobin, the A1C test provides an estimate of the average blood glucose over the previous 2-3 months.
A normal A1C is below 5.7%. An A1C between 5.7-6.4% indicates prediabetes. An A1C of 6.5% or above means diabetes. The higher the A1C, the poorer the blood glucose control.
Medications that can increase A1C
Several types of prescription medications may have the side effect of increasing blood glucose levels and consequently raising A1C values. Examples include:
Corticosteroids
Corticosteroids are anti-inflammatory medications used to treat conditions like asthma, arthritis, and inflammatory bowel disease. Examples include prednisone and dexamethasone.
Corticosteroids can increase glucose production by the liver as well as reduce the body’s ability to use insulin effectively. This results in higher circulating blood glucose.
Antipsychotics
Antipsychotic medications are used to treat conditions like schizophrenia, bipolar disorder, and depression. Examples include olanzapine (Zyprexa), risperidone (Risperdal), and quetiapine (Seroquel).
These medications increase insulin resistance, leading to elevated blood glucose. Weight gain is also a common side effect, which contributes to poorer glucose tolerance.
Beta blockers
Beta blockers are blood pressure medications that reduce the effects of adrenaline. Examples include metoprolol (Lopressor, Toprol-XL), atenolol (Tenormin), and carvedilol (Coreg).
Beta blockers may impair insulin secretion from the pancreas and reduce the body’s ability to respond to low glucose levels. This can result in slightly elevated glucose.
Thiazide diuretics
Thiazide diuretics are used to treat high blood pressure and edema. Examples include hydrochlorothiazide, chlorthalidone, and metolazone.
Thiazides cause the body to excrete more glucose into the urine. This results in a reduction in insulin secretion from the pancreas and a slight increase in blood glucose.
Second generation antipsychotics
Second generation (atypical) antipsychotics are used to treat conditions like schizophrenia, bipolar disorder and depression. Examples include clozapine (Clozaril), olanzapine (Zyprexa), and risperidone (Risperdal).
Like first generation antipsychotics, these medications increase insulin resistance and weight gain, resulting in higher circulating blood glucose.
Protease inhibitors
Protease inhibitors are anti-viral drugs used to treat HIV and hepatitis C. Examples include lopinavir/ritonavir (Kaletra) and telaprevir (Incivek).
Protease inhibitors can decrease the body’s ability to use insulin properly leading to insulin resistance and hyperglycemia.
Pentamidine
Pentamidine is an antimicrobial drug used to treat or prevent pneumonia in people with HIV. Pentamidine can cause pancreatitis, an inflammation of the pancreas. This impairs the pancreas’s ability to produce insulin, resulting in hyperglycemia.
Octreotide
Octreotide (Sandostatin) is used to treat acromegaly, a growth hormone disorder. It can alter pancreatic beta cell function and impair insulin secretion, leading to increased blood glucose.
Niacin
Niacin, also known as vitamin B3, is used to treat high cholesterol. Niacin can impair insulin release and reduce insulin sensitivity, resulting in higher blood glucose levels.
Glucocorticoids
Glucocorticoids like prednisone, dexamethasone and methylprednisolone are corticosteroid medications used to reduce inflammation in conditions like asthma, COPD, arthritis and inflammatory bowel disease.
Like other steroids, glucocorticoids increase glucose production in the liver, cause insulin resistance, and impair glucose uptake into cells. This results in elevated circulating blood glucose.
Atypical antipsychotics
Atypical or second generation antipsychotics used for schizophrenia, bipolar disorder and depression include clozapine (Clozaril), olanzapine (Zyprexa), aripiprazole (Abilify) and quetiapine (Seroquel).
These agents block dopamine receptors which can interfere with insulin receptor function, leading to insulin resistance and high blood sugars. Weight gain is also common, contributing to poorer glucose control.
Thyroid hormones
Thyroid hormones like levothyroxine (Synthroid, Levoxyl) and liothyronine (Cytomel) are used to treat hypothyroidism. Excess thyroid hormone increases glucose absorption from the gut and can reduce insulin sensitivity, resulting in hyperglycemia.
Antiretrovirals
Some HIV medications, known as antiretrovirals or antiretroviral therapy (ART), have been associated with insulin resistance and elevated blood glucose levels. Examples include protease inhibitors like ritonavir (Norvir).
Atypical antipsychotics
Atypical or second generation antipsychotic medications used to treat mental illnesses like schizophrenia and bipolar disorder may affect glucose metabolism, insulin secretion and increase weight, leading to higher blood sugars. Examples include olanzapine (Zyprexa) and clozapine (Clozaril).
Immunosuppressants
Immunosuppressant medications used after organ transplants can cause glucose intolerance and raise blood sugars. Examples include cyclosporine (Neoral, Gengraf), tacrolimus (Prograf) and sirolimus (Rapamune). The exact mechanisms are not fully understood but likely involve impaired insulin secretion and insulin resistance.
Some chemotherapy drugs
Some chemotherapy medications like L-asparaginase and glucocorticoids can affect insulin secretion and sensitivity, leading to increased blood glucose levels in cancer patients receiving these agents. Proper glucose monitoring and management are important during cancer treatment.
How medication impacts A1C results
The effects of these medications on blood glucose can vary from person to person based on the dosage, duration of therapy, and individual characteristics. However, as a general guideline:
– Corticosteroids, antipsychotics, and protease inhibitors may increase A1C by 0.5-2%
– Beta blockers, thiazides, and pentamidine may raise A1C by 0.25-0.5%.
– Other agents like niacin, octreotide, and thyroid hormones have smaller effects, potentially raising A1C by 0.1-0.3%.
Larger A1C increases are more likely with higher medication doses, longer duration of use, and having multiple glucose-raising medications. If A1C rises significantly, medication adjustments or changes may be required to optimize diabetes control.
Managing rising A1C due to medications
If your A1C increases due to glucose-raising medication effects, your healthcare provider will work with you to determine the best management plan. Steps may include:
Adjusting medication dosages
Your provider may consider lowering the dosage of the medication affecting glucose levels. This is only done if it does not compromise treatment of the condition the drug is meant to address.
Switching to alternative therapies
Substituting another medication in the same class without glucose effects may be an option. For example, switching from a sulfonylurea to metformin for type 2 diabetes. Or changing from a thiazide to a calcium channel blocker for hypertension.
Adding a glucose-lowering medication
If adjusting the dosage is not effective or feasible, an additional medication like metformin, insulin, or a GLP-1 agonist may be prescribed to help overcome the glucose-raising effects.
Increasing glucose monitoring
More frequent home blood glucose checks, continuous glucose monitoring, and A1C tests allow closer monitoring for medication adjustments. This helps tailor treatments to optimal effect.
Making lifestyle changes
Improving diet, increasing activity, losing weight if indicated, and implementing other beneficial lifestyle modifications can help counteract glucose-elevating medication effects.
Evaluating risks vs. benefits
Your healthcare team will weigh whether medication benefits outweigh risks of higher glucose. Some therapies may be discontinued if hyperglycemia becomes severe.
Medications that can lower A1C
While the medications described above can increase A1C, there are also many drugs that can lower A1C by improving glucose control in diabetes. These include:
Metformin
Metformin is a first line medication for type 2 diabetes. It lowers glucose production in the liver, delays glucose absorption, and improves insulin sensitivity. These effects help reduce A1C.
Sulfonylureas
Sulfonylureas like glipizide (Glucotrol) and glimepiride (Amaryl) increase insulin secretion from pancreatic beta cells. This lowers blood glucose and A1C.
Meglitinides
Meglitinides such as repaglinide (Prandin) and nateglinide (Starlix) also stimulate insulin release but are faster acting and shorter duration than sulfonylureas. They can lower A1C when taken before meals.
Thiazolidinediones
Thiazolidinediones like pioglitazone (Actos) improve insulin sensitivity in muscle and fat tissues, thereby reducing glucose and A1C.
DPP-4 inhibitors
DPP-4 inhibitors like sitagliptin (Januvia) inhibit the enzyme that breaks down GLP-1, allowing more of the hormone to stimulate insulin secretion and lower glucose levels and A1C.
GLP-1 receptor agonists
GLP-1 medications like liraglutide (Victoza) and exenatide (Byetta) act like the incretin hormone GLP-1. They stimulate insulin release, suppress glucagon, slow digestion, and promote weight loss to lower glucose and A1C.
SGLT2 inhibitors
SGLT2 inhibitors like empagliflozin (Jardiance) block glucose reabsorption by the kidneys, causing glucose excretion in urine to decrease blood glucose and A1C.
Insulin therapy
Insulin supplementation helps overcome insulin deficiency or resistance. Basal, bolus, and mixed insulin formulations lower glucose and A1C by improving insulin activity.
Pramlintide
Pramlintide (Symlin) is an injectable amylin analog that slows gastric emptying, improves glucose fluctuations, and decreases postprandial glucose rises to lower A1C. It is used with insulin.
Conclusion
A number of prescription medications can influence blood glucose control and lead to unwanted A1C increases. Being aware of these drugs and their potential effects on diabetes management is key. Monitoring glucose carefully and adjusting treatments accordingly under medical supervision can help achieve A1C goals despite medication challenges. Fortunately, many options exist to safely and effectively overcome medication-induced hyperglycemia.