To achieve good blood sugar control in the presence of failing kidney function is a difficult task for patient and doctor. There are various reasons for this.
In some people with diabetes the insulin sensitivity changes, for reasons that are often unclear: the tissues no longer respond as well to insulin. This can lead to a worsening of the diabetes.
Insulin - whether made by the body or injected as a drug - is partly broken down in the kidneys. When the kidneys are not functioning properly, less insulin is metabolized, so that the effect of the insulin is prolonged. This partially compensates for the reduced insulin sensitivity mentioned above, but can also result in hypoglycaemia -dangerously low blood sugar.
Someone who has advanced nephropathy often also suffers from other complications of diabetes. These may include damage to the nerves that regulate the gastrointestinal tract. Then food is no longer digested and absorbed properly. Typical signs are bloating, feeling full, irregular bowel movements, diarrhoea, nausea and vomiting. The irregular absorption of food can cause the blood sugar levels to swing violently.
Additionally, remember that many drugs, including those that reduce blood pressure, are excreted via the kidneys. If kidney function deteriorates and excretion does not occur properly, these drugs may persist in the circulation. This means that their effects are heightened and prolonged, which can lead to hypoglycaemia or other complications. Therefore, not all drugs are suitable for the treatment of people with impaired kidney function.
The drugs that should not be given include the biguanides, the most common of which is metformin. It is excreted exclusively via the kidneys and accumulates even in cases of mild kidney impairment. If the dose is too high, it can lead to life-threatening acidosis.
Many of the heavily prescribed sulphonylurea drugs are excreted via the kidneys, although in very different amounts. For nearly all preparations, the dose should be reduced (in consultation with a doctor) to avoid hypoglycaemia. An exception is gliquidone (Glurenorm®), of which only a small fraction is excreted by the kidneys.
There is a new generation of blood-lowering substances that includes repaglinide (NovoNor®) and nateglinide (Starlix®). These drugs are taken only at mealtimes and cause a short burst of insulin secretion that prevents a rise in blood sugar levels after eating. The drugs persist for only a short time in the blood. Repaglinide is broken down and excreted mainly (up to 92%) by the liver. Thus, it may be given to patients with impaired kidney function, as demonstrated in a recent study. Even in the presence of advanced kidney damage, blood sugar can be well controlled without an increased risk of hypoglycaemia. Nateglinide is also metabolized mainly in the liver and may therefore be given to patients with kidney failure. However, there are no large studies and no great experience with this drug as yet.
The newly introduced insulin-sensitizers, rosiglitazone (Avandia®) and pioglitazone (Actos®) improve diabetes control by making the tissues more responsive to insulin, so that the hormone works better.
What you can do for yourself:
Do everything you can, from diagnosis onwards, to keep your diabetes under control.
For people with Type 1 diabetes, this means that after the appropriate diabetes education, start intensive insulin therapy to keep your blood sugar level as normal as possible. It is advisable to join an experienced diabetes clinic. The state of the diabetes should be monitored regularly, including tests for typical diabetes complications. Repeat the diabetes education programme at regular intervals.
For people with Type 2 diabetes, the recommendations are specific to the individual because the disease expresses itself variably and alters with age. Naturally, in this case education and the effort to maintain blood sugar as near as possible to normal levels are still the most important. But the measures that need to be taken can vary:
a change in diet and lifestyle (for example, more exercise), blood sugar-lowering drugs or - and this shouldn't be put off too long -insulin injections. People with Type 2 diabetes should also be familiar with methods of self-management of blood sugar. Joining an experienced diabetes clinic for supervision and regular checking for diabetes complications is very important. In this case too, education should not be a one-off event.
When kidney function weakens, the diabetes worsens. A good diabetes education programme that covers the specific details pertaining to kidney impairment, as well as regular check-ups at the doctor's, mean that good metabolic control can be maintained - and this will help maintain your quality of life.
These drugs are broken down mainly in the liver; the resulting compounds are then excreted via the kidneys. Studies, admittedly on only a few patients, have shown that the drug profile does not rise in the presence of kidney failure.
People who inject insulin must also adjust their dose as soon as kidney function is impaired, because about half of insulin is metabolized in the kidneys. When these organs no longer work properly, insulin action is prolonged and the danger of hypoglycaemia rises. In patients with kidney damage, the most rapid-acting insulin possible should be used, because its effects can be controlled more easily.
Whether diabetic kidney disease develops quickly or slowly depends on the level of the blood pressure as well as on the level of the blood sugar. Low blood pressure can prevent or at least postpone the appearance and also the further development of kidney damage.
The methods for attaining normal blood pressure have improved continually in recent years. There are now many medicines available for the management of high blood pressure, whose effectiveness and also tolerability become better all the time. Patients can assess the success of the treatment themselves at home, using a blood pressure meter. Measuring your blood pressure over 24 hours provides a profile for the whole day and also the night, so that unwanted fluctuations can be discovered and targeted for treatment. Monitoring your own blood pressure is today a 'must' in the management of hypertension. As with blood sugar management, a high degree of self-responsibility is required of patients for therapy to be successful. But regular testing of your blood pressure and blood sugar level and taking tablets are worth the effort.
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