In kidney disease the same tests come back again and again: creatinine and eGFR for kidney function, urine albumin for leakage, and potassium, phosphate, calcium, PTH, haemoglobin and bicarbonate for what the kidneys regulate. Ranges vary a little between laboratories, and the trend over time says most.
By the Nyrami editorial teamPublished 10 August 2026Updated 2 October 20267 min read
A test result in kidney disease can have ten or twenty lines of abbreviations, numbers and small H and L flags. This page is a guide to the values you meet most often, what it can mean when they are high or low, and what you can ask your doctor. Three of them have their own, more detailed guides: eGFR, creatinine and albumin in the urine.
In chronic kidney disease there are two kinds of tests: those that measure how well the kidneys filter, and those that show whether the body can keep its salts, blood and acid in balance. The lower the eGFR, the more tests are taken, because high potassium, high phosphate, anaemia and too much acid in the blood become more common as kidney function falls.
Common tests in kidney disease
Creatinine
eGFR
Cystatin C
u-AKR (urine test)
Urea (carbamide)
Potassium
Phosphate
Calcium
PTH (parathyroid hormone)
Haemoglobin (Hb)
Bicarbonate (HCO3)
Creatinine, eGFR and albumin in the urine are the three measures of the kidneys themselves. eGFR is calculated from creatinine, age and sex, and is used to divide chronic kidney disease into stages. Albumin in the urine, measured as the albumin to creatinine ratio (u-AKR, often called ACR in English) in mg/mmol, shows whether the kidney filters are leaking, and is often the first sign of damage. Together they say most about how fast the disease may progress.
Read more in eGFR normal range, Creatinine normal range, Protein in urine and Stages of chronic kidney disease. You can work out your eGFR in the eGFR calculator.
Cystatin C is a small protein made by almost every cell in the body and filtered out by the kidneys. It is much less affected by muscle mass than creatinine. That is why it is used especially in people with little muscle, such as those over 80, children and people with a low body weight, and when eGFR is below 30 and medicine doses need adjusting. The laboratory then calculates a separate eGFR from cystatin C.
Cystatin C does not suit everyone. It is higher with an overactive thyroid, steroid treatment and pregnancy, and lower with an underactive thyroid.
Urea and carbamide are two names for the same substance (in Norwegian also urinstoff). It is a waste product made in the liver when the body breaks down protein, and the kidneys remove it in the urine. On Norwegian results it often appears as S-Urinstoff or P-Karbamid.
High urea can mean reduced kidney function, but it also rises with dehydration and when the body breaks down a lot of protein, for example with fever, after an operation or during bed rest. That is why it is always interpreted together with creatinine and eGFR. Low urea is seen in, among other things, liver failure and pregnancy.
Potassium is a salt that controls the muscles and the heart rhythm, and the kidneys are the main way out of the body. When kidney function is low, potassium can build up. Very high potassium can cause dangerous heart rhythm problems.
The reference range varies: hospital laboratories use about 3.5 to 4.6 mmol/l, while some private laboratories use 3.6 to 5.0. Check the range on your own result. A high result can also be false: Fürst states that the most common cause of high potassium on a result is poor handling of the sample during collection, storage or transport. Your doctor will then often repeat the test. ACE inhibitors and ARBs can also raise potassium. Read what you can do with food in Potassium in food.
Phosphate, calcium and PTH are linked and affect both the skeleton and the blood vessels. Phosphate leaves the body only through the kidneys, so it rises as kidney function falls. At the same time the kidneys are less able to make active vitamin D, and calcium can become low. The body responds by making more PTH, a hormone from the parathyroid glands in the neck. This is called secondary hyperparathyroidism.
In kidney failure it is common for PTH to be above the reference range. Helsedirektoratet writes that a PTH of two to three times the upper limit is accepted in kidney failure, but that high PTH over time increases bone turnover and the risk of fractures. High phosphate over time causes calcification in the blood vessels and raises the risk of heart and blood vessel disease. Treatment may include less phosphorus in food, phosphate binders with meals and active vitamin D, and it is managed by your kidney specialist. Read more in Phosphorus in food.
Anaemia, or low haemoglobin, is common in kidney failure because diseased kidneys make too little of the hormone erythropoietin (EPO), which tells the bone marrow to make red blood cells. The red blood cells also live for a shorter time. Anaemia can cause tiredness, breathlessness on exertion and less stamina.
Your doctor first looks for other causes, such as iron deficiency or bleeding. Iron stores are topped up, sometimes with iron into a vein, and if needed you get EPO as an injection. Helsedirektoratet recommends starting EPO before haemoglobin falls below 10 g/dl, with a target of 10 to 12 g/dl. It usually becomes relevant when eGFR is below 45. Ferritin and transferrin saturation are used to assess iron stores, but ferritin can be falsely high in kidney failure.
Low bicarbonate means there is too much acid in the blood, called metabolic acidosis. Healthy kidneys get rid of acid and hold on to bicarbonate, which is the body's buffer. In advanced kidney failure they cannot do this as well. The reference range is about 22 to 26 mmol/l.
The international KDIGO guideline recommends considering treatment when bicarbonate is below 18 mmol/l in adults, with tablets and sometimes changes to the diet. Treatment is followed with new tests, so that bicarbonate does not become too high.
A single test result is a snapshot. What says most about how things are going is the direction over time. An eGFR that stays stable at 45 for four years is a very different situation from one that has fallen from 60 to 45 in one year, even though today's number is the same.
Many values vary a little from one test to the next. Dehydration, an infection, a large meat meal or hard exercise can cause a temporary deviation. A small H or L does not always mean disease either: the reference range is set so that about one in twenty healthy people get a value outside it. Look at several results in a row, and ask your doctor what is normal for you.
How often you have tests depends on your eGFR, the amount of albumin in your urine and how fast the values change. With mildly reduced kidney function and little albumin, one check a year is often enough. The lower the eGFR and the more albumin, the more often you are checked, often several times a year. Everyone with diabetes should have eGFR and u-AKR at least once a year. See Stages of chronic kidney disease and Diabetic kidney disease.
For chest pain or severe breathlessness: call 113. Read more about the condition in Chronic kidney disease.
In the Nyrami app you can log eGFR, creatinine and albumin after each check-up and see the trend over time, so you can see the direction and know what to ask. If you have been given advice about potassium or phosphorus, the food scanner assesses potassium, phosphorus, sodium and protein in food for you. The app is free for iPhone and Android.
Turns the advice into something you can use in the shop and the kitchen: scan food and see potassium, phosphorus and salt assessed for you, and follow your numbers over time. Free on iPhone and Android.
A little foam when you pee is common and is usually caused by a strong stream, concentrated morning urine or toilet cleaner in the bowl. If your urine foams a lot every time for several days, especially if you have swelling, diabetes or high blood pressure, it may be protein. A urine test at your GP gives the answer.
In young adults, eGFR is usually above 90, often around 100 to 115, and it falls gradually with age. An eGFR between 60 and 89 is common in older people and does not mean kidney disease on its own. If eGFR stays below 60 for more than three months, it counts as chronic kidney disease (CKD), whatever your age.
Kidney disease rarely causes early symptoms, so it is found with two simple tests: a blood test that shows eGFR and a urine test that measures albumin (uACR). If you have diabetes, high blood pressure, heart or blood vessel disease, or kidney failure in the family, ask your GP for both, ideally every year.
