Lab Tests - Blood and Urine


Diabetes is a life-long condition. In order to stay on top of diabetes and its long term complications it is necessary to have a number of lab tests done at regular intervals. At least once every year you should have a thorough check-up, including several blood and urine tests, as part of your Annual Review. The tests will help you and members of your diabetes health care team to see how your diabetes management is going, and whether your diabetes is causing any additional health problems that require attention.

This page describes routine tests that, as a person with diabetes, you may have on a regular basis - at least once per year - regardless of any other health problems.

The section on "Complications" includes details of other tests that may be performed if you are referred for specialist care for problems related to having had diabetes for a number of years.




What's covered on this page


Tests for blood glucose control
Tests for kidney damage
Tests for cholesterol and lipid profile
Tests for thyroid function

Tests for liver function


 

Tests for blood glucose control

HbA1c

HbA1c is the most common way of measuring blood glucose control. This is a blood test that gives an indication of average blood glucose levels over the previous 6 weeks to 3 months.

 

HbA1c

Blood Glucose*

Comments

Poor

control

> 8%

Frequent and/or prolonged episodes of hyperglycaemia where blood glucose levels > 10 mmol/l

  • Consider increasing SMBG
  • Does treatment plan need revising?

Reasonable

control

7 - 8 %

Before meals:

4.4 - 7.0 mmol/l

1 - 2 hr after meals:

< 10 mmol/l

  • Individual treatment goals should always take into account the patient's ability to understand and perform SMBG

Intensive / Tight

control

< 7 %

Before meals:

4.4 - 6.0 mmol/l

1 - 2 hr after meals:

< 8.0 mmol/l

  • Consider increased risk of hypoglycaemia
  • Particularly important in pregnancy
  • This degree of control is inappropriate for some people, especially the very young or old, those at risk of severe hypoglycaemia and those with advanced kidney or heart disease

* These blood glucose values are suggested target ranges based on current recommendations in the literature. They are, by necessity, generalised for the diabetic population as a whole.

>> More on HbA1c

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Fructosamine

Another test that is sometimes used to give a more short-term indication of blood glucose control is fructosamine. However, although fructosamine is a cheaper test, and may be useful in some circumstances,* the major draweback of using it on a routine basis is that in obese people with Type 2 diabetes the test often gives falsely low results. It is also reduced in conditions in which there is a high turnover of the protein albumin, such as in diabetic kidney disease.

*Fructosamine can be useful indicator of blood glucose control during pregnancy, when short-term changes in diabetes managment and control indices have a greater significance. The reference range is lower for pregnant women as tight control is required.

Reference range for serum fructosamine:

during pregnancy:

190 - 300 umol/L

< 200 umol/L

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Blood glucose

Your blood sample will also be tested for a fasting blood glucose, which is of most value for people with Type 2 diabetes - it gives some indication of baseline blood glucose control before a 'glucose challenge' (i.e. a meal).

Reference range for fasting plasma glucose
in people with diagnosed diabetes:
4.0 - 6.0 mmol/L

 

Blood glucose tests for the DIAGNOSIS of diabetes is covered in the introductory section, "What is Diabetes?"

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Tests for kidney damage

Microalbuminuria and Proteinuria

Diabetic kidney disease ('nephropathy') is first detected in its very early stages when small amounts of protein appear in the urine. The protein is mostly albumin and the condition is known as microalbuminuria. The term proteinuria is a general term used to describe protein in the urine.

You may be asked to take an early morning sample of urine with you or you may need to make an overnight collection or 24 hour collection. Your urine sample may be tested for protein at the surgery or clinic by a simple dip-stick method. An overnight or 24-hour collection will be sent to the laboratory for a more accurate measurement.

Small amounts of protein may leak into the urine for a number of reasons - so, if your test proves positive, the doctor will first want to rule out causes other than diabetic kidney damage; infection and strenuous exercise can both cause temporary proteinuria. You should be tested again on one or two further occasions to confirm a positive test.

Reference range for proteinuria
normal: < 20 ug/min
Proteinuria = protein in the urine

Microalbuminuria

20 - 200 ug/min

30 - 300 mg/24hr

30 - 300 mg/g*

Macroalbuminuria

> 200 ug/min

> 300 mg/24hr

> 300 mg/g*

*Albumin:creatinine ratio

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Creatinine and Creatinine Clearance

Another basic screening test for kidney function is a simple blood test for a substance called creatinine. This is a protein substance produced by muscles. It is released into the bloodstream at a constant rate and removed by the kidneys. A high level of creatinine in the blood can be a sign of kidney damage. A series of serum creatinine levels over time gives a measure of variation in glomerular filtration rate and can show the decline of kidney function in diabetic nephropathy. [See the section on Diabetic kidney disease ('nephropathy') for more on the pathology of the disease process.]

Sometimes the blood test is accompanied by a timed urine collection and the amount of creatinine being removed by the kidneys is calculated. This is known as a creatinine clearance test. Creatinine clearance can be used as a measure of glomerular filtration rate (GFR).

Creatinine clearance can be estimated from serum creatinine using a special formula (Cockroft and Gault) without the need for a urine collection.

 

Reference ranges for serum creatinine:

teenager/young adult

adult female

adult male

0.040 - 0.090 mmol/L

0.050 - 0.105 mmol/L

0.060 - 0.120 mmol/L

Reference ranges for urinary creatinine:

adult female

adult male

4.0 - 17.0 mmol/day

7.0 - 24.0 mmol/day

Reference ranges for creatinine clearance*:

adult female

adult male

> 1.2
ml/sec/1.73m2

>1.5
ml/sec/1.73m2

NOTES RE REFERENCE RANGES


*after about 40 yrs of age, creatinine clearance drops by about 0.1
ml/sec/1.73m2 every ten years

There is considerable variation of creatinine levels between individuals, depending on age, sex, and body build (especially muscle). As a result, it is more meaningful to compare test values against a reference to the individual's own range, rather than to a population range.

 

LOOK AFTER YOUR KIDNEYS!

Good blood glucose control and good blood pressure control can slow or prevent the development of diabetic kidney disease.

If detected early, nephropathy can be effectively treated and you need not go on to develop kidney failure. Keep your diabetes well controlled and make sure that you remember to take your urine sample when you attend your check-up or go to the laboratory for tests.

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Tests for cholesterol and lipid profile

What is a lipid profile? A lipid profile is a group of tests that together help to determine the risk of macrovascular (major blood vessel) disease, and, more specifically, coronory heart disease.

A lipid profile measures values for total cholesterol, HDL-cholesterol ("good" cholesterol), and triglycerides, and a value for LDL-cholesterol ("bad cholesterol") is usually determined from these. Other calculated values that may be reported include Cholesterol/HDL ratio, or a risk score based on lipid profile results, age, sex, and other risk factors.

For more on cardiovascular risk, risk factors, and coronary heart disease, see parts 1-4 of section on "heart disease"

Total cholesterol

Total cholesterol comprises different 'types' that are separated according to their density. High density lipoproteins are 'good'; lower density lipoproteins are not.

Reference range for Total cholesterol:
<5.0 mmol/L

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HDL cholesterol

High HDL cholesterol levels are protective against atherosclerosis. A low HDL is an independent risk factor for cardiovascular disease.

Reference range for HDL cholesterol:
(females 0.3 mmol/L higher)
1.0 - 2.5 mmol/L

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Triglycerides

Non-fasting specimens (see below): According to Medlab, 90% of normal people have a non-fasting triglyceride of <1.8 mmol/L, which is within the acceptable range, even for fasting, and makes the 'inconvenience' of fasting unnecessary. Of course, 'normal' people don't have diabetes...

Fasting specimens (>8 hours after food): The above comment not withstanding, it is usual to measure triglyceride in the fasting state, and with abstention from alcohol for the previous 24 hours.

Reference range for fasting triglycerides :
< 2.0 mmol/L

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LDL cholesterol

LDL cholesterol is calculated from a standard formula* using the measured values of total cholesterol, HDL cholesterol and fasting triglycerides.

*NOTE: The formula is not accurate, especially for high triglyceride levels (>4.5)

The main factors that determine LDL cholesterol levels are

  • genetics (not modifiable by lifestyle change)
  • diet (modifiable)

LDL cholesterol is said to make up about 80 percent of the total cholesterol in the 'average' person; for this reason, total and LDL cholesterol levels are not always distinguished between.

Reference range for LDL cholesterol:
(as recommended by New Zealand National Heart Foundation)
<3.0 mmol/L
PEOPLE WITH DIABETES Reference range for LDL cholesterol:
(as recommended by Diabetes New Zealand)
<2.5 mmol/L

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Cholesterol / HDL ratio

A convenient way of expressing relative lipid values is the ratio of total cholesterol to HDL cholesterol.

Reference range for Total / HDL cholesterol:
<4.5 mmol/L

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FASTING - or not??

According to Diagnostic Medlab, Total and HDL can be non-fasting, but for the calculation of LDL cholesterol, triglycerides should be fasting. Medlab state that, "a point worth making is that for a person eating a healthy low fat breakfast or lunch, there will be no significant difference between fasting and non-fasting." Of course, in this case, the 'person' referred to is not one with diabetes...

A sensible approach might be to make the first profile non-fasting; if levels are higher than ideal, a second fasting specimen could be ordered to complete the baseline. Agreed, this might not be appropriate for many Type 2's in which a fasting glucose obtained at the same time is often informative... But for those people on insulin, especially those with Type 1 diabetes, a non-fasting sample is far more practical. The ramifications of delaying breakfast and (or not) delaying morning insulin can be imagined... Speaking from experience, I sometimes wonder, "Is it worth the hassle?!" (KMR 2007)

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Tests for thyroid function

Autoimmune thyroiditis ("Hashimoto's") is one of the most common autoimmune disorders of the endocrine system, and is frequently associated with autoimmune (Type 1A) diabetes. Measurement of thyroid-stimulating hormone (TSH) levels is recommended as a cost-effective screen in people with exisitng Type 1A diabetes.

TSH levels are raised and thyroid hormone levels are usually lowered (see note below) in autoimmune thyroid disease, which ultimately causes hypothyroidism.

Reference range for Thyroid stimulating hormone (TSH):
0.4 - 4.0 mU/L
Reference range for Free thyroxine (T4):
10 - 24 pmol/L
Reference range for Free tri-iodothyronine (T3):
2.5 - 5.5 pmol/L
TSH is the first choice for thyroid screening; a level between 0.4 and 5 mU/L gives 99% exclusion of hypothyroidism.
The term 'subclinical hypothyroidism' is used to describe people with a mildly underactive thyroid. Typically such people would have a TSH between 5 and 10 and a T4 in the 8-16 range.

NOTE: In the early stages of autoimmune thyroid disease (Hashimoto's) thyroid hormones are released into the bloodstream causing elevated levels in the short term (mild thyrotoxicosis). Ultimately, however, thyroid hormones (T3 and T4) are low as permanent hypothyroidism develops.

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Tests for liver function

Liver enzyme elevations are common in association with poor glycaemic control, obesity, hypertriglyceridaemia and "fatty liver" or non-alcoholic steatohepatitis (NASH).

Mild chronic elevations of the aminotransferases (ALT and AST) < 250 U/L are common in people with Type 2 diabetes, and often reflect an underlying insulin resistance.

Reference range for alanine aminotransferase (ALT):
*35 - 45 U/L
Reference range for aspartate aminotransferase (AST):
*5 - 45 Ul/L
Reference range for alkaline phosphatase (ALP):
*25 - 100-130 U/L
Reference range for gamma-glutamyl transpeptidase (GGT):
*0 - 60 U/L
Reference range for bilirubin :
5 - 20 umolL
*age and sex dependent

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Diabetes is a life-long condition. In order to stay on top of diabetes Diabetes is a life-long condition. In order to stay on top of diabetes and its long term complications it is necessary to have a number of lab tests done at regular intervals. At least once every year you should have a thorough check-up, including several blood and urine tests, as part of your Annual Review. The tests will help you and members of your diabetes health care team to see how your diabetes management is going, and whether your diabetes is causing any additional health problems that require attention.and its long term complications it is necessary to have a number of lab tests done at regular intervals. At least once every year you should have a thorough check-up, including several blood and urine tests, as part of your Annual Review. The tests will help you and members of your diabetes health care team to see how your diabetes management is going, and whether your diabetes is causing any additional health problems that require attention.Diabetes is a life-long condition. In order to stay on top of diabetes and its long term complications it is necessary to have a number of lab tests done at regular intervals. At least once every year you should have a thorough check-up, including several blood and urine tests, as part of your Annual Review. The tests will help you and members of your diabetes health care team to see how your diabetes management is going, and whether your diabetes is causing any additional health problems that require attention.