by Jessica Pyhtila, PharmD, BCPS, BCGP
At first, it may seem strange that diabetes can lead to kidney disease. However, diabetes is the most common cause of severe kidney disease in the United States. Further, kidney disease occurs in up to 40% of people with diabetes. The metabolic changes in your body when you have diabetes can create a situation where your kidney function begins to suffer. For this reason, it is important to be aware of the relationship between diabetes and kidney disease, and how to best control your risk factors for kidney problems.
Why Diabetes Causes Kidney Disease
Diabetic kidney disease is the result of the complex metabolic changes in your body when you have diabetes, including high blood pressure and high blood sugar. Over time, these can damage the blood vessels and waste filtration mechanism in your kidneys, leading to permanent damage.
Without intervention, diabetic kidney disease can worsen and lead to other complications like high blood pressure, increasing your risk of cardiovascular problems. Worsened kidney problems can lead to end-stage renal disease, or ESRD, which often requires dialysis. Within 20 years of diabetic kidney disease onset, around 20% of people with Type 2 diabetes and more than 75% of people with Type 1 diabetes will have ESRD.
Checking for Kidney Disease When You Have Diabetes
Your doctor can order several different tests to check your kidney function. Experts recommend these tests be performed at least once annually to monitor kidney function. These tests include:
- Urine albumin test: This urine test is also known as a “spot urine”, a “microalbumin” or a “spot urinary albumin-to-creatinine ratio” test. Albumin is an important protein in your body. Normally, healthy kidneys filter albumin from the urine. However, when kidney damage is present, protein spills into the urine. Albumin is one of the first proteins that can be found in the urine under these circumstances. The more kidney damage that is present, the more protein is found in the urine. Protein in the urine is known as albuminuria, a condition which is considered to be a risk factor for worsening kidney function and cardiovascular disease.
- Glomerular filtration rate, or GFR: This blood test indicates how well your kidneys are working. The glomeruli are filters in your kidneys that allow waste to be removed. As your kidney function worsens, the glomeruli become less efficient. The GFR test shows how quickly your glomeruli can remove waste products. The lower the GFR, the more impaired the kidneys. Importantly, multiple variables are considered when calculating your GFR, including your age, sex, and race.
It can be tempting to avoid medical check-ups if you are concerned about getting unpleasant news. However, it is important to stay up to date with your doctor’s appointments when you have diabetes. As your kidney function changes, the kinds of medications you can safely take will change, as may the medication doses. For example, certain common medications like metformin should be avoided if you have severe kidney problems due to an increased risk of serious side effects like lactic acidosis. Further, although kidney damage cannot be reversed, monitoring the extent of the damage can help your doctor choose treatments to slow the progression of kidney problems.
Managing Diabetic Kidney Disease
Treating diabetic kidney disease often involves controlling the medical conditions that would otherwise cause it to worsen. Management strategies include:
- Controlling blood sugar: Studies show that poor blood sugar control is linked to worsening diabetic kidney disease. However, your goal blood sugar numbers will vary depending on your medical history. Your doctor will be able to advise you on the blood sugar goals you should target.
- Controlling blood pressure: High blood pressure, or hypertension, is known to worsen kidney function. Hypertension often results from diabetic kidney disease in people with Type 1 diabetes. Although high blood pressure frequently co-occurs with diabetes in those with the Type 2 form of the disease, high blood pressure can also worsen diabetic kidney disease. Controlling high blood pressure can preserve kidney function and lead to a longer life expectancy. Although the blood pressure goal for people with diabetes is generally less than 140/90 mmHg, this can vary. As such, your doctor will be able to advise you on your target blood pressure.
- Lifestyle modifications: Exercise, weight loss, and reducing salt intake can help prevent diabetic kidney disease from worsening. Specifically, salt should be limited to no more than 2 grams daily. Smoking cessation and controlled cholesterol levels are also recommended by kidney experts.
- Protein restriction: Limiting your daily protein intake may help preserve kidney function in some people with diabetic kidney disease. Your daily protein intake should be 0.8 grams per kilogram of body weight, which roughly converts to 0.03 ounces per 2.2 pounds of body weight. For example, a 220-pound person should have a protein intake of approximately 3 ounces a day. Dropping below this quantity does not appear affect kidney function.
Medications That May Help Diabetic Kidney Disease
Although no medication can reverse kidney damage, multiple medications have a direct action on the kidneys and have been shown to slow or prevent a decline in kidney function. These include:
- Certain blood pressure medications: Two classes of blood pressure medications are strongly recommended in diabetes treatment guidelines for helping to prevent and slow diabetic kidney disease. These are angiotensin converting enzyme inhibitors, or ACEIs, and angiotensin II receptor blockers, or ARBs. ACEIs include many blood pressure medications ending in “-pril” like lisinopril (Prinivil, Zestril, Qbrelis) and enalapril (Epaned, Vasotec). ARBs include blood pressure medications ending in “-sartan” like losartan (Cozaar) and valsartan (Diovan). However, ACEIs and ARBs should not be used at the same time due to an increased risk of side effects like high blood potassium levels, and lack of benefit from the combination.
- Certain diabetes medications: Two classes of diabetes medications appear to have a direct effect on kidney health. These include sodium–glucose cotransporter 2 inhibitors, or SGLT2is. Medications in this class have names ending in “-flozin” such as empagliflozin (Jardiance) and canagliflozin (Invokana). Glucagon-like peptide 1 receptor agonists, or GLP1as, also can help to protect kidney function. GLP1as have names ending in “-glutide” like semaglutide (Ozempic) and dulaglutide (Trulicity). Importantly, SGLT2is and GLP1as can be used together.
Although diabetic kidney disease cannot be reversed, it can be treated. By working with your doctor to keep your diabetes, blood pressure, and lifestyle risk factors under control, you can help prevent further kidney damage.
References
Food and Drug Administration. “FDA revises warnings regarding use of the diabetes medicine metformin in certain patients with reduced kidney function.” April 8, 2016. Retrieved from https://www.fda.gov/media/96771/download
LabTestsOnline. “Urine Albumin and Albumin to Creatinine Ratio.” August 12, 2020. Retrieved from https://labtestsonline.org/tests/urine-albumin-and-albumin-creatinine-ratio
American Diabetes Association. “Microvascular Complications and Foot Care: Standards of Medical Care in Diabetes−2020.” Diabetes Care, January 2020. Retrieved from https://care.diabetesjournals.org/content/43/Supplement_1/S135
LabTestsOnline. “Estimated Glomerular Filtration Rate (eGFR).” September 8, 2020. Retrieved from https://labtestsonline.org/tests/estimated-glomerular-filtration-rate-egfr
American Diabetes Association. “Diabetic Nephropathy.” Diabetes Care, January 2003. Retrieved from https://care.diabetesjournals.org/content/26/suppl_1/s94
Kidney International. “KDIGO 2020 Clinical Practice Guideline for Diabetes Management in Chronic Kidney Disease.” October 1, 2020. Retrieved from https://www.kidney-international.org/action/showPdf?pii=S0085-2538%2820%2930718-3
