BMP/CMP Beyond The Basics electrolytes, kidney and liver tests - ChartCure.com, ⚙🔑🩸 Understand Your medical Record

Blood chemistry tests include the basic metabolic profile (BMP) and comprehensive metabolic profile (CMP). The CMP adds a few tests to the BMP, mostly related to liver function.

Note that the values provided below for normal and abnormal test results are approximate and will vary by laboratory. People differ in the presence or absence of symptoms that occur at any abnormal blood test level.

SODIUM (Na)

Interpretation:

	MILD	MODERATE	SEVERE	CRITICAL
LOW	129-133	125-128	120-124	<120
HIGH	146-149	150-159	160-169	>169

LOW SODIUM LEVEL (HYPONATREMIA)

MILD HYPONATREMIA

There are no symptoms from mildly low Na and it is not dangerous.
Commonly seen with dehydration after vomiting or diarrhea.
If it is from dehydration and you are not vomiting, oral electrolyte rehydrating fluids may be all you need. Your kidneys will take care of the rest.
Of course, any of the more serious causes of low Na (sections below) can cause mild hyponatremia early in their course.
No further evaluation may be needed.
If the cause is unknown, a sodium level should be checked again in a few days to make sure it is not getting lower.
Once the cause is removed, your body will correct the level to normal.
Mildly low Na can be “normal” (baseline level) for some people, particularly the elderly.

MODERATE HYPONATREMIA

This degree of low sodium often does not cause any symptoms itself, although you are more likely to have symptoms from whatever is causing it.
If symptoms occur they are usually nonspecific weakness, lethargy, or muscle cramps.
Before giving a large amount of saline your provider may want to do more tests to help determine the cause of your low Na, if not already obvious.
Otherwise, all of the considerations for MILD hyponatremia also apply to MODERATE.
Hospital admission is sometimes indicated.
Importantly, if your level is in this range it must be watched very carefully to make sure it does not fall any lower. This usually requires hospital admission.
A common cause is “SIADH,” which causes your body to retain water out of proportion to salt, thus diluting your blood.
SIADH is often an adverse reaction to a medication, particularly some diuretics, but many other medications can cause this, as can many illnesses.
Other common causes of low Na include severe congestive heart failure or cirrhosis of the liver. These diagnoses are usually obvious and already known. Excessive water drinking can cause low Na.

SEVERE HYPONATREMIA

All of the considerations for Mild and MODERATE hyponatremia still apply, including the common causes.
Confusion or abnormal mental status may develop
However specific sodium-related symptoms may still be absent or mild.
Symptoms severity depends on how rapidly the condition developed.
Even if there are no symptoms, this requires admission to the hospital for treatment and a definitive determination of the cause.

CRITICAL HYPONATREMIA (<120)

This should always be considered a potentially life-threatening abnormality, even if there are no or minimal symptoms.
Symptoms are more likely to be severe but still vary considerably depending on how fast the sodium level became very low.
Seizures can occur and require immediate treatment to raise the Na level.
Even if there are no symptoms, extreme care and expertise are required to raise the sodium level slowly towards normal. This often requires ICU admission.
If not corrected slowly the treatment itself can be very dangerous.

HIGH SODIUM LEVEL (hypernatremia)

MILD HIGH HYPERNATREMIA (146-149)

By far the most common cause is dehydration.
Besides thirst, there may be no symptoms from the high Na.
The treatment is to stop the cause (vomiting, diarrhea, sweating, etc.) and rehydration by oral or IV fluids.
The kidneys will then correct the level.
Why do some people get high Na with dehydration and others develop low Na? It mostly depends on their access to, and ability to drink, water.

MODERATE (150-159) AND SEVERE HYPERNATREMIA (160-169)

Gradual weakness and depressed mental status will develop over this range.
Severe dehydration is present
Often there is an initial cause, such as a stroke or infection, which causes the patient to be unable to eat or drink, leading to dehydration and hypernatremia.
Much less commonly, hypernatremia in this range can be due to the effects of medications, the lack of antidiuretic hormone, or kidney problems causing the loss of water.
Hospital admission and hydration with IV fluids are indicated.

CRITICAL HYPERNATREMIA (>169)

All comments above for Moderate-Severe high Na still apply.
The patient is often poorly responsive or comatose.
Extreme care must be taken when lowering the Na level to avoid the complication of brain swelling. ICU admission may be indicated.

UNDERSTANDING SODIUM

Sodium, along with Chloride, make up table salt. Just as salt dissolves in water, salts are dissolved in your blood and their components can be measured.
Na is critically important to most body functions and therefore there are many things that can make your blood level abnormal. Likewise, abnormal levels can cause problems with many-body systems.
You may have noted that dehydration can cause high or low sodium levels. Which occurs depends on one’s access to, and ability to drink, water.
Also, beware that high glucose levels “falsely” decrease the measured Na value. Each time your glucose level goes up by 100 mg/dl (to 200, 300, etc.) the glucose reading will be lower by 1.8 mmol/Liter.
The main ways animals control sodium levels are through 1) control of thirst 2) The kidneys regulating the retention (holding on to) or excretion (letting go in the urine) of sodium and water.
Antidiuretic Hormone (ADH) is released from your brain and tells your kidneys how much water to hold onto. Many factors, including many medications, can alter this process leading to abnormal Na levels.
Sodium is critical to the conduction of nerve impulses. Symptoms from abnormal Na levels are usually related to this. Either high or low levels can cause general weakness, fatigue, confusion, seizures (particularly low values), and abnormal mental states from lethargy to coma.

CHLORIDE (Cl)

INTERPRETATION KEY POINTS

Abnormal chloride levels are very common. Usually, this is a result of loss from vomiting, sweating, diuretics.
Chloride levels will fall or rise, like sodium levels, if you have excessively diluted or concentrated blood from water gain or loss.
Increasing or decreasing Cl levels are also a normal compensating response to excessive loss or gain of another electrolyte. This occurs with diarrhea but also with chronic breathing disorders such as COPD and other acid-base disturbances.
Minor abnormalities are usually of no importance themselves
Abnormal chloride levels are usually not a primary issue requiring targeted treatment (unlike sodium). People don’t get put in the hospital or treated for low chloride alone. The treatment is usually aimed at another disorder that is causing the abnormal Cl level.
There are no specific symptoms caused by abnormal chloride levels alone, in the absence of some other electrolyte abnormality.
The Cl level gives important information for interpreting the cause of other specific electrolyte and acid-base abnormalities and helps determine the type of IV fluids that are most appropriate.

UNDERSTANDING CHLORIDE

Chloride regulation is closely tied to Na regulation. Even severely abnormal chloride levels are usually not a primary issue requiring targeted treatment (as opposed to Na). Rather they tend to follow along and react to other electrolyte and blood chemistry abnormalities.
Negatively charged Cl-, and positively charged Na+, bind together and form common table salt (NaCl). In your blood, Na+ is the main positively charged dissolved electrolyte (cation) and Cl- is the major negatively charged electrolyte (anion). But there are other important negative ions (anions) to consider besides Cl-. These include bicarbonate (HCO3-) and others which are present only under abnormal conditions or severe illness.
The bottom line is that your blood has to keep a balance between positively charged cations (which are acidic) and negative anions (basic). If they were not in balance your blood would be “charged.” Not shockingly, the body tries to avoid this. The balance between positively charged cations and negative anions also determines the acid-base balance of your blood.
So abnormal chloride is frequently a compensating response to excessive loss or gain of another electrolyte, particularly bicarbonate (HCO3-, which is a basic anion). If there is excess production of some other negatively charged anion, This most often occurs with vomiting and diarrhea but also with chronic breathing disorders such as COPD and from diuretic medications.

POTASSIUM

	MILD	MODERATE	SEVERE	CRITICAL
HIGH	5.3-5.5	5.6-6.1	6.2-6.5	>6.5
LOW	3.0-3.4	2.5-3	<2.5

LOW POTASSIUM (HYPOKALEMIA)

MILD AND MODERATE HYPOKALEMIA (LOW POTASSIUM)

Mild low K levels are a very common finding and not a serious problem.
Common causes of low potassium are vomiting, diarrhea, heavy alcohol use, starvation, diuretic medications, and excessive sweating from heat or exercise.
Muscle cramps or palpitations may occur in some people and these are generally not dangerous.
To correct a mildly low K, sometimes all that is needed is a good meal, and to stop the source of potassium loss.
Moderately low may cause symptoms such as weakness, muscle cramps, and palpitations. It may cause abnormal heart rhythms in those who are predisposed.
IV potassium is often given in the moderate range.

SEVERE HYPOKALEMIA

SEVERELY LOW K+ levels (around 2.5 meq/L or less) always need treatment, with intravenous potassium infusions. These low levels can cause serious heart rhythm disturbances and severe muscle weakness.

HIGH POTASSIUM (HYPERKALEMIA)

MILD AND MODERATE HYPERKALEMIA

First, make sure the report doesn’t state “hemolysis,” or “hemolyzed” specimine. This indicates the high potassium level is, at least in part, due to blood cells breaking up during collection. The result is not accurate and a fresh sample must be tested.
Common causes of high potassium levels include poor kidney function, some diuretics (Aldactone, triamterene) common blood pressure medications such as Lisinopril and Valsartan (ACE and ARB classified medications).
MILD AND MODERATE ELEVATED levels up to around 6.2 usually don’t cause symptoms
But even MILDLY ELEVATED K+ levels should prompt careful consideration of the cause, and close follow-up with repeat tests to make sure it is not rising. Don’t ignore this.
MODERATE AND SEVERE HIGH K+ levels always need prompt treatment. If you are at home, an ER visit is indicated.
SEVERE HYPERKALEMIA, over about 6.2 often requires emergency intravenous medications, and sometimes hemodialysis.
CRITICALLY HIGH potassium causes life-threatening heart rhythm disturbances. An EKG should be obtained to look for any warning signs that these may occur soon.
Whether you have complications from a high potassium level is in part related to how rapidly it became elevated.

UNDERSTANDING POTASSIUM

Potassium (K+) is another tightly controlled anion in your blood. Like sodium, it is involved in almost all body functions, down to the level of cell function.
Your body is very efficient at controlling levels. If you eat or take too much, the kidneys get rid of it and you urinate it out (assuming your kidneys are functioning well). If you don’t take in enough, or lose potassium due to diarrhea, vomiting, or diuretic medications, your kidneys will try to pull back more K+ into your blood.
Dietary replacement is about more than bananas. A medium banana contains about 11 meq of potassium. A medium-sized baked potato with skin has around 24 meq. 6 oz of orange juice gives 9.4 meq. Many foods are potassium-rich and the internet is full of information on these.
People with poor kidney function can potentially “overdose” by eating too many potassium-containing foods.
Once the cause of low potassium is stopped (diarrhea, vomiting, diuretic, medication) your body is good at fixing it with a normal diet. But sometimes extra potassium is needed to increase levels quickly.

CARBON DIOXIDE (CO2)

INTERPRETATION KEY POINTS

Understanding CO2 is complex, there is no simple explanation.
The test measures two forms of CO2: dissolved gas CO2 and CO2 which has been converted to bicarbonate (HCO3-). Collectively these are the main factors in determining if your blood acid/base balance is normal.
Some of the CO2 in your blood converts to hydrogen ions (H+) and bicarbonate ions (HCO3-). H+ is acid and bicarbonate is a base.
MILD HIGH OR LOW CO2 is common and often inconsequential, particularly if your anion gap (AG, see below) is normal. Levels need to be interpreted in the context of the AG.
People with acute or chronic kidney disease often have low CO2 levels on a BMP.
Low CO2 with a high AG may represent a serious disorder such as sepsis or diabetic ketoacidosis. This combination of findings should not be ignored.
Low CO2 occurs with diarrhea due to loss of bicarbonate in the stools. In this case, the AG should be normal.
High CO2 occurs with vomiting due to an increase in your blood bicarbonate level. Bicarbonate is a base, vomit contains stomach acid.
High CO2 levels may be seen with severe COPD or when CO2 can’t be removed from the lungs due to ineffective breathing (respiration).
Most of the time abnormal CO2 levels are not a specific target for treatment.
Treatment, if any is directed towards treating the underlying cause, not by giving medications to correct the level. This can be done by giving the correct fluids, stopping the vomiting or diarrhea, or improving breathing (lung ventilation).
In some cases of CRITICALLY LOW CO2 bicarbonate infusions may be needed.
A blood gas analysis test may be needed to determine if the CO2 abnormality is overwhelming your body’s ability to maintain a safe Acid-Base (Ph) status.

UNDERSTANDING CO2 (AND BICARBONATE)

CO2 and HCO3- are in a state of equilibrium, one converting to the other and visa-versa and the balance between the two is affected by many things.
HCO3- is the negatively charged (anion) part of baking soda (NaHCO3-). It is an important buffer in your blood, helping maintain your acid and base balance.
Maintaining a normal Acid-Base balance (Ph) is critically important to cell function.
In your blood, bicarbonate and carbon dioxide are in equilibrium, they are really two forms of the same thing
The serum chemistry (BMP/CMP) lab test does not distinguish between these two forms, it measures both together.
So if you aren’t breathing off enough CO2 (poor lung ventilation such as with severe COPD), this will build up in your blood. Some of that is converted to carbonic acid, which is hydrogen + bicarbonate. This will cause the bicarb level to be increased but your blood becomes more acidic due to the extra hydrogen ions.
Yes, it is complex.
A blood gas analysis is frequently required to understand a major abnormality of HCO3- or an acid/base abnormality
The blood gas gives separate values for dissolved CO2 and bicarbonate
Under most circumstances, your body keeps your blood from getting too acid or too basic (keeps the Ph around 7.4)
Except in severe cases, it achieves this because blood has a good buffer capacity from other ion’s and proteins, by increasing your breathing rate to decrease your CO2, and over time the kidney can retain or remove acid and base to help correct the abnormalities.

CALCIUM

Before you go on

MAKE SURE YOU KNOW IF YOUR RESULT IS A TOTAL CALCIUM OR AN IONIZED CALCIUM LEVEL.
CHECK YOUR LAB’S UNITS OF MEASUREMENT (mmol/L or Mg/dL)

SOME KEY CONCEPTS FOR UNDERSTANDING CALCIUM

Total Calcium is a proxy measurement for Ionized Calcium.
It is Ionized Calcium that affects your metabolism and which is responsible for any symptoms from high or low Ca.
Much of the time the Total Calcium is a good approximation for Ionized Ca.
But not always for the following reason
HIgh or more commonly low, blood proteins (albumin) will cause the Total Calcium to not accurately reflect the Ionized Ca level (which is the more important factor).
The Total Calcium test measures calcium which is bound to albumin and other proteins AND the Calcium which is dissolved in your blood, the ionized calcium.
So if your albumin is low your total calcium will necessarily be reduced, but the important ionized calcium level may still be normal, low, or potentially high.
If the total calcium is significantly abnormal you must either measure the ionized calcium or your provider can make a calculation to estimate the effect of low albumin on your total level.

Just to confuse things, there are also different units used to report Calcium levels and it depends on your lab. They can be reported as either mmol/L or mg/dL. Make sure you are looking at the correct one when reviewing these notes.
Make sure to check the reference range for normal and abnormal for your particular lab.
Calcium measurements are subject to error due to improper handling of the blood sample
Leaving a tourniquet on your arm for a few minutes before the blood is collected can change the result.
If the reported level does not make sense based on the symptoms or medical history, it should be repeated before any action is taken.

HIGH CALCIUM LEVELS (HYPERCALCEMIA)

Normal and abnormal ranges vary by lab and there are not well-defined cutoffs for MILD, MODERATE, or SEVERE. This is a rough categorization. Symptoms and severity of illness are really the most important thing dictating if treatment is needed.

	TOTAL Ca	IONIZED Ca
Mild high	10.5-11.9 (mg/dL) 2.6-3.0 (mmol/L)	1.32-3 (mmol/L)
Moderate HIgh	12.0-13.9 (mg/dL) 3.1-3.5 (mmol/L)	3.1-3.5 (mmol/L)
Severe High	>14 (mg/dL) >3.5 (mmol/L)	>3.5 (mmol/L)

MILDLY ELEVATED CALCIUM

There are usually no symptoms from Mild Ca elevations
The cause needs to be investigated and the level monitored to make sure it does not persist or go higher.
It is not urgent to treat the level and try to bring it back to normal very rapidly.
Persistent elevations can cause kidney stone formation.

MODERATELY HIGH CA

This should never be ignored, the cause should be determined promptly.
Generally requires treatment and very close monitoring.
Symptoms are none or mild and include weakness, body aches, constipation, and dehydration.
Treatment may be as simple as giving IV fluids and giving diuretics or it may require specific medications, depending on the symptoms.

SEVERELY ELEVATED CALCIUM

This requires emergency treatment and hospital admission
Often causes confusion, weakness, lethargy, dehydration, kidney failure, coma, heart rhythm problems.

LOW CALCIUM (HYPOCALCEMIA)

IONIZED Ca

TOTAL Ca

NORMAL

1.15-1.29 (mM/L)

4.61-5.17 (mg/dL)

2.25-2.6 (mmol/L)

8.8-10.5 (mg/dL)

Mild Low

1.0-1.14 (mM/L)

4.0-4.6 (mg/dL)

2.0-2.14 (mmol/L)

8.0-8.7 (mg/dL)

Mod. Low

0.8-0.99 (mM/L)

3.2-3.9 (mg/dL)

1.75-1.9 (mmol/L)

7.0-7.9 (mg/dL)

Severe Low

0.66–.79 (mmol/L)

2.65-3.19 (mg/dL)

1.5-1.74 (mmol/L)

6.0-6.9 (mg/dL)

Critical Low

<.66 (mmol/L)

<2.65 (mg/dL)

<1.5 (mmol/L)

<6 (mg/dl)

INTERPRETING LOW CALCIUM LEVELS

Be sure it is not an artifact from a low albumin level
MILDLY low Ca levels usually do not cause symptoms
MODERATELY LOW Ca may cause symptoms or may have none.
Symptoms of MODERATE to SEVERLY low Ca range from tingling sensations around the mouth or in the hands and feet, twitching, muscle cramps, or in very severe cases constant spasm (tetany).
If symptoms are present or in SEVERE HYPOCALCEMIA intravenous calcium should be given.
Most often low Ca levels are not due to a lack of calcium in the body or the diet.
Usually, it is caused by some other disorder of your electrolytes or acid-base balance.
In that case, the treatment is to correct whatever other disturbance is causing the low calcium level and supplemental calcium may be given but is not always necessary.
A telltale sign of low Ca is a spasm of the hand when a blood pressure cuff is inflated.
For persistent moderate to severe hypocalcemia, the cause should be investigated, if not already obvious.

UNDERSTANDING CALCIUM

High or low dietary intake of calcium (or of vitamin D) is a very uncommon cause of abnormal calcium blood levels in Western society.
Regulation of blood ionized calcium levels is normally under tight control by parathyroid hormone. The kidney is also involved in blood level control.
Many factors will temporarily affect Ca levels.
These include other electrolyte abnormalities, medications, dehydration, hyperventilation, acid-base disturbances, kidney function, and thyroid problems, blood transfusions, to name but a few.
A persistently abnormal calcium level (after the other temporary disturbances are excluded or treated) is frequently due to abnormal parathyroid gland function.
Calcium is normally under tight control by parathyroid hormone (PTH) and other hormonal and kidney mechanisms.
Chronic kidney disease is a common cause of low blood calcium values.
Several types of cancer can cause high Ca levels.

ANION GAP (AG)

INTERPRETATION KEY POINTS

This is a calculation based on electrolytes (Na, Cl, K) and your bicarbonate level.
A high AG indicates there is something is causing extra acid production in your blood.
A slight elevation (1-3) above normal is not uncommon with dehydration or when someone has not taken in enough calories and is starting to burn fat stores for energy. For example with a “keto” diet where fat is metabolized to keto-acids.
An elevated AG should always be recognized by your doctor and they should always consider the possible causes.
An elevated AG may represent the presence of a severe illness. Common causes are severe infections (sepsis causing lactic acid production) and a severe lack of insulin in diabetics (diabetic ketoacidosis from the breakdown of fats into ketones). There are many other potentially serious causes.

SECTION 2: KIDNEY FUNCTION TESTS

BLOOD UREA NITROGEN (BUN)

BUN is a product of normal protein metabolism. BUN is formed in your liver.
As a lab test its measurement helps evaluate your hydration and your kidney function
The function of BUN is to excrete excess nitrogen from your blood. It gets filtered out of your blood by the kidneys and is excreted in the urine.
The most common causes of elevated BUN are dehydration and a decreased kidney function.
Anything that reduces blood flow to your kidneys can increase BUN. Examples are dehydration, heart failure, and shock from any cause.
BUN levels generally cause no symptoms until quite elevated, roughly 80-120 depending on the individual.
Very high levels cause “Uremic Syndrome.” Symptoms include weakness, nausea, skin changes, and most concerning abnormal mental function from mild cognitive difficulties to severe confusion.
A large excess in dietary protein can also elevate BUN, as can bleeding in your stomach (due to protein in digested blood).
A low BUN poses no danger itself but can be a marker of other problems. It can occur from poor nutrition, liver disease, and if you are very well hydrated. BUN is often on the low in late pregnancy due to water retention.
For further information see the kidney function overview section below

SERUM CREATININE (Cr)

This is also a waste product of normal metabolism
Elevated levels indicate poor kidney function.
Dehydration can also increase the Cr level, as is the case with BUN levels.
Calculating the ratio of BUN/Cr (BUN level divided by the Cr level) sometimes helps to decide if an elevated creatinine is due to a damaged kidney or dehydration. If this ratio is greater than 40 it suggests dehydration. If less than 20 it suggests a kidney problem.
A low body muscle mass may cause a low Cr level.
For further information see the kidney function overview section below

ESTIMATED GLOMERULAR FILTRATION RATE (eGFR) [BMP/CMP]

This is the preferred measure of kidney function and it is used to define the stages of chronic renal failure.
Any single measurement may not accurately tell your permanent kidney function because many things can temporarily change the eGFR.
eGFR is a calculation based on your creatinine level, your age, gender and race. As such, it is an estimate.
The stages (1-5) of kidney function or failure are defined as follows:

Normal >90%
Mild 89%-60%
Moderate to Severe 59%-30%
Severe 29%-15%
Kidney Failuare <15%

For further information see the kidney function overview section below

KIDNEY FUNCTION OVERVIEW

Creatinine is produced from the breakdown of proteins as part of normal metabolism.
The kidney filters blood and removes waste products, including creatinine and BUN.
The kidney structures which do this are called “glomeruli.”
The Glomerular Filtration Rate tells how efficiently your blood is being cleaned, eg filtered.
eGFR is a calculation based on the Cr level.
If your kidneys aren’t filtering well creatinine builds up in your blood.
The Cr is not dangerous itself, it is just a marker of kidney function.
Because creatinine is related to protein, and because much of your body protein is in muscle, Cr levels are higher in people with a lot of muscle mass, and lower in the frail and elderly.
Thus the eGFR calculation on your lab report, which is based on average for your age, gender and race, may not be perfectly accurate if your muscle mass is not average.
eGFR will underestimate your true kidney function if you have a large muscle mass.
A high intake of protein in the diet, or creatine supplementation, will also raise your Cr level, making your eGFR appear lower than otherwise.
Many things that are not kidney damage can temporarily raise your Cr level and hence lower the reported eGFR.
For example, if less blood goes to your kidney, for any reason, then less blood is filtered. In that case, your creatinine goes up and your eGFR calculation goes down, with time.
This is what occurs when you are dehydrated. Less water in your blood means less volume pumped to the kidney, the Cr goes up.
The same effect occurs if your heart is very weak and can’t pump enough blood to the kidneys or if your blood pressure is low for any reason.
Some medications can interfere with the removal of creatinine by the kidneys, even though they don’t actually injury the kidneys.
The same effect occurs with BUN but its rise is proportionally higher. Thus if abnormal kidney function is related to dehydration the ratio of BUN/CR goes up. If this is >20 it is suggestive (not diagnostic) of dehydration. If <20 more likely a kidney malfunction.
For example if the BUN=60 and Cr=2 the ration is 60/2=30 suggestive of dehydration (or bleeding in the stomach).