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February 2017

Are My Buns Too High? A Layman's Guide to the CMP

This ever happen to you? You just got your blood test results, and noted that a few items were flagged as "out of range." Your bun is too high! You albumin is low! Suddenly you feel ill. What's wrong?  Do you have cancer? Are you going to die soon?  Should you make your will?
Bunx pix

Stay calm, take some deep breaths, call the doctor's office.

The nurse answers your concern with, "Doctor will discuss these results at your clinic visit in 2 weeks!"

Two weeks?  You could die by then! What to do next?

First of all, don't panic. If you are feeling the same as ever, and the doctor said these were routine screening tests, it probably CAN wait for the two-week visit. On the other hand, if you were seeing a doctor about a new health problem, and she ordered these tests to help diagnose you, do NOT use this guide. You need to follow up with your doctor.

But if you're curious, and maybe just a little bit worried, you can use this handy layman's guide to see if your "abnormal" tests are significant.  First, we'll look at the CMP (comprehensive medical panel).  In a future post we'll do the CBC (Complete Blood Count.)

The CMP measures the blood level of several salts, proteins and chemicals. Why these items? Because they are the main components of blood serum, they are at fairly high levels, and are easy to measure in an automated machine.

Each test result gives the blood level (ignore the units) and a range for "average" results, for 95% of the population. Be aware this means 5% of normal, healthy people may be outside of the average range on any test--and it could be you.

The results of the test are printed out using standard abbreviations, such as K (potassium), glob (Globulins), and BUN (blood urea nitrogen). And by the way, BUN is pronounced as individual letters. B.U.N.  NOT "bun" as in "hamburger."  It makes me cringe to hear a patient say "bun" instead of its acronym, B.U.N.

You don't need to be fasting to get these blood tests, although many people mistakenly think you do, and put themselves through a lot of discomfort. If, on the other hand, your doctor wants to get an accurate measure of your fasting blood sugar, or of your cholesterol and lipids, then you will need to fast as requested.

When I order these tests as a routine screen, I pay attention to only three or four results. The rest can usually be ignored on the first pass, though they might be helpful to me to interpret a problem. Remember that a lot of tests can give false results because the machine is not properly aligned, the tourniquet was on too tight, the blood was kept too long before it was tested, etc., so don't be concerned unless the test is in Category 1 and is very much out of range.

Here is my interpretation guide for a patient's screening blood tests. I've omitted the reference rage, because it will be on the report. Using this guide, if you have an abnormal Category 1 test, your doctor should be in touch with you. Category 2 can wait a few days, and may require a repeat.  The "ignorable" are just that.

CATEGORY 1.   MOST IMPORTANT TESTS

K, Potassium.

The potassium in your blood is important in conducting electrical impulses in your heart and nerves, so your body keeps it within a fairly tight range for your heart to beat regularly, and for your nerves to function. The kidneys quickly pee out any excesses, unless you are taking a medication to prevent this.  Too high a level (greater than 7) can be fatal, and can be caused by medications, kidney failure, cancer treatment, or taking potassium supplements or salt substitutes especially in combination with blood pressure medication.  A slightly elevated potassium level is not dangerous and can be a false reading due to leaving the tourniquet on too long when drawing blood, or to abnormalities in the blood cells, or may require adjustment of your medication.  A low potassium can be due to excess sweating (such as running a marathon), taking a diuretic for blood pressure, or diarrhea and vomiting.  A slightly low potassium is not dangerous and can be corrected with pills or diet--there's lots of potassium in fruit including tomatoes and bananas.  Low potassium can contribute to leg cramps or to feeling down. A very low potassium can be dangerous.

Cr, Creatinine

Creatinine is a breakdown product of muscle that your body makes which is disposed by the kidneys. It is used as a measure of kidney function--the lower it is, the better the function. Creatinine increases as you and your kidneys age, so it's important to compare it to your last few CMP tests to see if has significantly changed. It can appear high when you are dehydrated, but this usually goes back to normal. If it is high further testing and evaluation may be needed, but if it is very high you may need to be hospitalized.  

Bili, Bilirubin

This is a breakdown product of red blood cells that is disposed by the liver in the form of bile.  It can be elevated due to a diseased liver, or a blockage of the bile duct, hepatitis, or destruction of blood cells (hemolysis). Some people have a hereditary slightly elevated bili; it's called "Gilbert's syndrome" and it's harmless. Your doctor can sort out an elevated bili by looking your other tests on the CMP and the CBC. Further testing may be needed.  If your bili is very high your eyes will be yellow, and you need medical attention soon.

Glu, glucose.  

A high blood sugar is the most likely test to be found to be abnormal in a routine screen in a person without any apparent health problems. A blood sugar above 125 is significant if you were fasting before your blood draw; it may or not be significant if you ate within a few hours. Your doctor may to do some additional tests to determine if you have diabetes or pre-diabetes. A very high blood sugar (above 400) needs prompt attention and may put your in the hospital. A blood sugar below average is not a medical emergency unless you are taking a diabetes medication; a sugar below 50 is unusual without medication but can be serious.

CATEGORY 2: SOMEWHAT IMPORTANT (Ignore unless very abnormal)

Na, Sodium

Your body regulates the sodium level so the salt in your blood is approximately similar to that in seawater. This happens by concentrating or diluting the serum by regulating thirst and drinking water, or peeing excess salt, or storing salt as salt water in the legs (edema). You can tolerate a pretty wide range of sodium level without any serious effects, and your body will self-correct most of the time because you have a large storage reserve, so taking salt pills won't really help it. Sometimes the abnormal sodium is due to a medication you are taking, or a hormone or kidney imbalance, and your doctor will be aware of this.      

Ca, calcium

Your body has pounds of reserve calcium in your bones, and uses it to regulate your blood calcium level by adding or subtracting, regulated by a few hormones. That is why the blood level of calcium does not help in determining whether or not you have osteoporosis (thin bones).  A very high calcium (2 or 3 points above average) can cause symptoms such as tiredness, constipation, and even mental confusion. It is serious, and it can be due to a hormone imbalance, some forms of cancer, or to taking calcium pills with excessive vitamin D. Slightly elevated calcium may or may not be serious.  A low calcium level can be due to a hormone imbalance.

Caution: Ca can be hard to interpret because the measured level also depends on your blood proteins. Low albumin is one of the most common causes of falsely low calcium. A high calcium can be caused by a blood technician leaving the tourniquet on too long.

B.U.N., Bun, or Blood Urea Nitrogen

B.U.N. is a measure of the urea in your system which, like creatinine, is cleared out by the kidneys. It can also be a measure of kidney function but it's not very helpful to the doctor, since it can be elevated for many reasons, including fasting or dehydration. A low Bun can mean starvation, or it can be normal for you. Best not to over-read it.

3. IGNORE

The following blood tests are rarely abnormal on their own. They are used mostly to interpret other abnormal blood test results.  We won't review in detail.

ALB albumin.  This is your major blood protein.

AGAP, anion gap. The anion gap is the gap or difference between the total level of potassium + sodium, minus the total of chloride + bicarbonate. A very high gap can mean there is another "unknown" ion. The AGAP may be elevated in some forms of poisoning, or with some medications or drugs.

Cl, chloride:  a salt which balances the sodium in your blood.

Bicarb, Carb, or Bicarbonate: a salt which balances your sodium. It is the water-soluble form of carbon dioxide.

AST or GOT: a protein in liver tissue, and its level can help to sort out a liver inflammation or high bilirubin.

ALT or GPT. a protein in liver tissue, and its level can help to sort out a liver inflammation or high bilirubin.

Glob, Globulin: The group of blood proteins known as antibodies which fight disease.

These are your blood test results, in a nutshell. I hope this blog reassured you somewhat. Remember, don't panic.  Call the doctor's office if you are still concerned about your results.