Chronic kidney disease and its impact on blood sugar

The kidney is involved in both glucose production and insulin clearance from our body, thereby playing a vital role in managing blood glucose levels in our blood. As a result, any adverse effect on the functioning of the kidneys especially Chronic Kidney Disease (CKD) will have a direct bearing on our blood sugar levels. It also increases the risk of diabetes and related health complications including severe episodes of hypoglycemia which, if not managed properly, could lead to serious health consequences.

How do the kidneys work?

Kidney, the filtration unit of the body, drains out excess fluids and minerals from the system. It also plays a major role in maintaining the acid-base homeostasis (internal balance) in the bloodstream that is responsible for the body’s physiological functions.

Each kidney consists of about a million filtering units called nephrons. Each nephron includes a filter, called the glomerulus, and a tubule. The nephrons work in a two-step process: the glomerulus filters the blood, and the tubule returns the required substances to the blood and removes excess water and minerals from the body.

Types of kidney complications

Dr Garima Agarwal, nephrologist, Manipal Hospitals, Bengaluru, says broadly two types of kidney complications can happen: 

• Acute kidney complications: These are sudden injuries that lead to immediate kidney damage.
• Chronic kidney disease (CKD): Any kind of kidney damage that has crossed three months is called chronic. Typically, hypoglycemia is seen in individuals with CKD.

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Renal multitasking: insulin metabolism and glucose production

The body’s glucose-production process (gluconeogenesis) is maintained by the liver and kidneys. It is important for maintaining blood glucose levels during prolonged periods of fasting or when the consumed diet is not providing the enough glucose. Dr Pankaj Agarwal, consultant endocrinologist, Hormone Care and Research Centre, Ghaziabad, Uttar Pradesh, says the liver and kidneys are responsible for producing glucose from non-carbohydrate sources inside the body. When these two organs fail in their functioning, there is a higher risk of hypoglycemia.

Normally, the kidneys ensure that excess insulin gets filtered out of the body after carrying out its function of breaking down blood glucose. But this function goes haywire in case of kidney impairment.

Risk of low blood sugar and kidney disease

“The majority of people with diabetes are at a high risk of slipping into chronic kidney damage over time,” says Dr Garima. “Hence, they are at the higher risk of developing hypoglycemia.” This (risk of hypoglycemia) could be because of the following reasons:

• Whether it is natural insulin or external insulin, if there is kidney failure, insulin doesn’t get metabolised since it stays longer than usual in the body — leading to a drop in blood sugar levels.
• Any kind of kidney disease decreases the ability of the body to create its own glucose (which helps in maintaining sugar levels, so a person doesn’t slip into hypoglycemia).
• In case of diabetic patients who aren’t aware of their failing kidney function and who keep on consuming their diabetes medicines, which stay in the body for longer than usual and which can lead to low blood sugar levels. A dosage adjustment is required in case of diabetes if they are showing signs of a decrease in blood sugar levels.

Some other medications too can have the side effect of lowering blood sugar levels.

Food pattern and frequency-induced hypoglycemia

Dr Mahesh DM, consultant, endocrinology, Aster CMI Hospital, Bengaluru, says that patients with chronic kidney problems are at risk for low blood sugar because of changes in appetite and meal routine.

According to an article published in BMC Nephrology in January 2022, olfactory (sense of smell) input plays an important role in a meal’s flavour, sensory appeal of food and food enjoyment. A dysfunction in smell leads to food aversion, decreased appetite and inadequate food intake, which predisposes an individual with CKD to poor nutritional status and malnutrition.

Dr Suma Lata Nayak, director and unit head, nephrology, Fortis Hospital, Delhi, lists the common causes of low blood sugar among people with CKD:

• Missing meals or not taking them on time
• Inadequate food intake due to poor appetite
• Excess dosage of insulin or diabetes medication
• Administering insulin shots or diabetes medicine at the wrong time.
• Consuming alcohol.

Symptoms to watch out for kidney health

To identify if there is a failing kidney function, Dr Garima says the following symptoms should be watched out for:

• Sudden lower blood sugar levels: Diabetics can suddenly start having low blood sugar levels without any changes in medication and lifestyle. This is an indication of kidney complications.
• Having frequent low blood sugar episodes
• Switching from no blood pressure to high blood pressure
• Urine froth: It is a sign of protein leakage in urine.
• Foot swelling: It is a sign the kidneys are working less since the water that should have been excreted is retained in the body.
• Nausea
• Loss of appetite
• Low hemoglobin levels: At times people with risk factors such as diabetes and hypertension will have low hemoglobin. Hence they must check their kidney functions too since low hemoglobin could be an indicator of failing kidney health.
• Breathing difficulty: It could be because of the water retention in lungs due to non-optimum kidney function and, at times, due to hypertension.

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Basic screening tests for kidney health

The basic and cost-effective screening tests to track kidney health are:

• Urine test: To detect the presence of protein
• Creatinine: It is a marker of kidney function. High levels indicate kidney damage.
• Hemoglobin test: It is an indirect indicator of kidney damage.

“People with high-risk factors like diabetes and hypertension or with a family history of kidney diseases like cystic diseases must screen at least once a year,” says Dr Garima. She adds that people with no risk factors but who are above 45 years must screen once annually.

Precautions for kidney health

Dr Garima says the following precautions can be taken to keep an eye on the kidneys:

• Staying well-hydrated (people without risk factors)
• Not taking over-the-counter medication — for example, painkillers — since they damage the kidneys
• Not smoking
• Keeping blood pressure in check
• Keeping weight in check (people without risk factors)
• Getting basic screening done for early detection
• Exercising regularly
• Controlling blood sugar levels (people with risk factors like diabetes and hypertension).

A general dietary recommendation for people with kidney disease is to reduce their protein and salt intake, she adds.