Diabetics get a lot of blood tests done and sometimes we should ask for others. Here they are broken down so you know what you are getting done and what you should ask for.
Summary at the end for those who find the article tl;dr.
‘Sugariness’ And Insulin Measures
HbA1c
Practically every diabetic knows their HbA1c (Hemoglobin A1c). This is a measure of the number of hemoglobin proteins in the blood with glucose attached. This gives an indication of how sugary a person’s blood has been for the last three months.
Why three months? Hemoglobin is part of your blood’s red blood cells. In a healthy human, red blood cells survive for around three months in the blood before dying.
This has a few implications. Firstly, if you have a disease which affects the life of your red blood cells, such as anemia, this will throw off your HbA1c measure, shortening the time over which the HbA1c is a representative average. Also, the measure is not a linear average; the result is biased to the more recent ‘sugariness’ because not every red blood cell lives for exactly three months. Not all of those ‘born’ three months ago will be around but most of the one born a month ago will.
It should be noted that there is around a 10% relative error in this test so if you have, say, an HbA1c of 7% and it moves on your next test by less than 0.7%, this could be nothing more than measurement error.
Finally, while a lot of emphasis is put on the HbA1c, it is only a number to indicate your average blood glucose level (BGL); it says nothing of the fluctuations. Some doctors will get nervous at lower HbA1c results because they have no visibility of the fluctuations. If you have excellent blood glucose control do not be afraid of lower HbA1c results.
C-Peptide
When beta cells produce insulin they actually produce a thing called proinsulin which is two halves of the insulin molecule and a ‘connecting peptide’ (c-peptide) which joins them. Through the magic of biology this eventually transforms into insulin and a residual c-peptide molecule.
By measuring the amount of c-peptide in the blood we can get an indication of how much insulin the pancreas is producing (injected insulin is not in the form of proinsulin so there is no c-peptide residue).
A typical Type 2 will have a high c-peptide reading because their pancreas is trying to overcome their insulin resistance. A typical Type 1 will have a low c-peptide because the immune system has destroyed their beta cells and with it the ability to produce proinsulin. I say typical because for a LADA like me with insulin resistance, my c-peptide is normal/high even though I am Type 1.
Fasting Insulin
This measures the level of insulin in the blood for a fasting individual. Unlike c-peptide this cannot distinguish between insulin made by the body and injected insulin.
Fasting Glucose
The blood sugar level when fasting. For an individual producing enough insulin to keep their liver in check, this should be normal.
HOMA-IR/HOMA-β
The ‘Homeostatic Model Assessment of Insulin Resistance’ (HOMA-IR) and the ‘Homeostasis Model Assessment of β-Cell Function’ (HOMA-β) are mathematical formulae using the blood’s (fasting) insulin and glucose levels to give an indication of the individual’s insulin resistance and beta cell function.
In other words, for someone not using insulin, their fasting insulin and glucose results can be used to determine how much insulin resistance they have and how much beta cell function they still have.
Vitamin D
Linked to insulin sensitivity, this may be useful to see if you are low (many of us office workers are).
Vitamin B12/Active B12
If you are taking Metformin/Diabex/Glucophage (different names for the same thing), you should check your B12 levels as Metformin can affect the body’s ability of absorb vitamin B12 from food. The difference between ‘B12’ and ‘Active B12’ is that, while different forms of B12 are circulating in the blood only the ‘active’ form can be used by cells in the body.
Autoantibodies Against Islet Cells (ICA), GAD, IA2, ZnT8, and Insulin
This is the definitive test for determining if someone is a Type 1 diabetic as it proves the immune system is attacking the body’s insulin production machinery.
If this test is positive, you are Type 1, by definition. However, there are people with all the hallmarks of Type 1 diabetes who do not get a positive result on autoantibody tests. Possible reasons for this include:
- The person has had Type 1 diabetes for so long that there are no longer any beta cells left to provoke an immune response
- Their Type 1 diabetes is caused by an as yet unknown autoantibody
Whether these ‘idiopathic’ Type 1s should be classified as Type 1, given the lack of autoimmunity evidence, is a matter of debate but, from a treatment perspective, it makes sense to align them to ‘classic’ Type 1s.
Body Mass Index and Waist Measurement
While not blood tests, the Body Mass Index (BMI) and a person’s waist measurement give a general indication of obesity. Obesity is linked to insulin resistance so, in an ideal world, diabetics of any Type would stay within a healthy weight range.
Oral Glucose Tolerance Test (OGTT)
Although I never had one of these myself (presenting with mild DKA at diagnosis was enough to establish I had diabetes), it is something often used to determine if a person has diabetes.
The test is relatively simple: the patient, who has fasted, is given a fixed measure of glucose syrup and blood is taken at the one, two, and maybe the three hour mark to measure the patient’s glucose response. If the patient cannot bring the blood glucose levels down fast enough and they go too high, the patient is diabetic.
Heart and Kidney Disease
Diabetics, due to damage from high BGLs, are prone to kidney disease and have a higher rate of heart disease, compared to the general population
Blood Pressure
Not a blood test, but the test the doctor does with the arm band and an air pump. A high blood pressure can be a risk factor for kidney and heart disease.
Albumin/Creatinine Ratio
This is a urine test and, for healthy functioning kidneys, there should be little to no albumin in the urine. It is measured as a ratio because creatinine is generated at a reasonably constant rate in the body so, if creatinine fluctuates in urine, this is likely due to relative levels of hydration in the body. So, by measuring the ratio, we get a stable indicator of albumin in the urine, independent of hydration levels.
Cholesterol (LDL/HDL/Triglycerides)
The prevailing thinking in conventional medicine is that the different types of cholesterol play a role in a person’s risk of heart disease. A metastudy (review/compilation of multiple actual studies) in 2016 found the evidence for this was not strong. I am not going to settle this debate in this blog article so discuss this with your health care team and do your own research if it is important to you.
For myself, I eat a lowish carbohydrate diet which means I have moved to eating more proteins and fats. My thinking is that, even if there is an increased risk of long term heart disease, this is outweighed by my short term desire to preserve my beta cells and remain insulin free for as long as I can, while keeping my BGLs in a healthy range.
Assuming cholesterol measures are relevant to a person’s heart health, here are the measures on interest:
- Total cholesterol: ideally low
- LDL: ideally low
- HDL: ideally high
- Triglycerides: ideally low
- Cholesterol/HDL ratio: ideally low i.e. you want relatively low cholesterol or high HDL with the absolute amount being less important (useful for diets higher in fat)
- LDL/HDL ratio: ideally low based on the above and again, talks at relative levels, rather than absolute levels
Sodium
High levels of sodium can indicate kidney dysfunction.
Bicarbonate
This is a measure of how acidic your blood is (low levels suggest more acidic blood). Again, this can be an indicator of kidney health but, be warned, if you are engaging in a low carbohydrate diet and producing ketones, these are acidic and may throw off the test. I have seen this in my test results on occasion.
The idea that one blood test can be the result of one of many causes speaks to the need to get multiple tests done to confirm something like kidney disease. While my blood may sometimes be slightly acidic, my albumin/creatinine ratio is always within range, confirming it is my keto-like diet that is the cause and not organ damage.
Urea
Like the bicarbonate test, urea can be indicative of a number of things. Most importantly it can indicate kidney damage or heart failure. Urea in the blood is a result of protein breakdown so, again, if you are engaging in a low carbohydrate diet and eating more protein, a higher urea level may be the cause. It is no coincidence that on those blood tests where my bicarbonate was low, my urea was also high and was indicative of nothing more than me being a little more keto than usual.
Liver Disease
The other organ that gets a battering from diabetes is the liver. We have a raft of tests available to us to ensure our liver is doing its job and keeping us healthy.
Gamma Glutamyltransferase (GGT)/ Lactate Dehydrogenase (LD, LDH)/ Aspartate Aminotransferase (AST)/ Alanine Transaminase (ALT)
These are enzymes found in the liver and usually only in small amounts in the blood. An elevated level of them in the blood can indicate kidney damage. It can also indicate a bumpy ride on a motorcycle leading up to the test so always regard blood test results with caution until confirmation tests have been conducted.
Total Protein
This is related to the Albumin/Creatinine test as Albumin is a protein. Abnormal total protein levels in the blood can indicate kidney damage but can also indicate liver disease. A high protein diet has no effect on protein in the blood.
Globulin
Total Protein = Albumin + Globulin so, again this is a protein test where abnormal results can indicate kidney or liver disease, among other things.
Alpha-Fetoprotein
Another protein test which can test for severe liver disorders in non-pregnant people.
Infection Markers
White Cell Count/ Lymphocytes/ Eosinophils/ Monocytes
Lymphocytes, Eosinophils, and Monocytes are all types of white blood cells. All of these can be tested to get an idea of infections, allergies, and other disorders which may be affecting the body.
While I occasionally have elevated levels of these, it generally settles down by the time of my next quarterly/biannual blood test. If it did not, it could be indicative of an undiagnosed prevailing condition e.g. cancer or infection and would warrant further investigation.
tl;dr
Here is the list of common blood (and other) tests done for diabetics and their meaning.
- ‘Sugariness’ and Insulin Measures
- HbA1c: An average of your last three months of blood sugars
- C-Peptide: A measure of how much insulin your body is still producing
- Fasting Insulin: How much insulin is in your blood to keep your liver in check
- Fasting Glucose: How sugary you are without food
- HOMA-IR/HOMA-β: Mathematical formulae using the fasting insulin and glucose used to determine insulin resistance levels and beta cell function
- Vitamin D: Low levels can contribute to insulin resistance
- Vitamin B12/Active B12: B12 absorption can be hindered by diabetic medications such as metformin
- Autoantibodies Against Islet Cells (ICA), GAD, IA2, ZnT8, and Insulin: Tests whether diabetes is caused by an autoimmune response and is therefore Type 1 diabetes
- Body Mass Index and Waist Measurement: Body measurement tests to give an indication of obesity and potential insulin resistance
- Oral Glucose Tolerance Test (OGTT): A test involving the drinking of glucose syrup to assess whether a person is a diabetic
- Heart and Kidney Disease
- Blood Pressure: The test with the armband and pump. This can indicate an increased risk of heart and kidney disease
- Albumin/Creatinine Ratio: A urine test for kidney health
- Cholesterol (LDL/HDL/Triglycerides): Measures of fatty acids and fatty acid transporters in the blood. Abnormal levels are traditionally considered a risk factor for heart disease
- Sodium: High levels can indicate kidney disease
- Bicarbonate: Low levels can indicate kidney disease but can also result from a ketogenic diet
- Urea: Used as an indicator for heart or kidney disease but can also be indicative of a high protein diet
- Liver Disease
- Gamma Glutamyltransferase (GGT)/ Lactate Dehydrogenase (LD, LDH)/ Aspartate Aminotransferase (AST)/ Alanine Transaminase (ALT): Liver enzymes not usually found in the blood which can indicate liver damage
- Total Protein: Abnormal levels can indicate liver or kidney damage. Not affected by dietary protein intake
- Globulin: Abnormal levels can indicate liver or kidney disease
- Alpha-Fetoprotein: Can indicate severe liver damage/disease
- Infection Markers
- White Cell Count/ Lymphocytes/ Eosinophils/ Monocytes: White cell tests which can indicate infection, allergy or disease.
The Practical Diabetic 