A basic metabolic panel (BMP) measures eight substances in your blood that reflect how well your kidneys are working, whether your blood sugar is normal, and whether your body’s fluid and mineral balance is on track. When you get your results back, you’ll see each of these eight values listed alongside a reference range. A value inside that range is generally normal; one outside it deserves a closer look. Here’s how to make sense of each number.
The Eight Values on Your BMP
Every BMP reports the same eight measurements, which fall into four groups: blood sugar, calcium, electrolytes (sodium, potassium, chloride, and CO2/bicarbonate), and kidney waste products (BUN and creatinine). Labs print a reference range next to each result, and those ranges can vary slightly from one lab to another. The ranges below come from the American Board of Internal Medicine and represent the most widely accepted standards.
Glucose: Your Blood Sugar Snapshot
The normal fasting glucose range is 70 to 99 mg/dL. If your doctor ordered the BMP as a fasting test and your result lands at 100 or above, that’s worth paying attention to. A fasting glucose between 100 and 125 mg/dL falls into the prediabetes range. A result of 126 mg/dL or higher on two separate tests is the threshold for a diabetes diagnosis.
If you weren’t fasting, your glucose will naturally be higher, and your doctor will interpret it differently. Keep in mind that certain medications can also shift this number. Acetaminophen can cause falsely elevated readings on continuous glucose monitors, and some antibiotics like ciprofloxacin and levofloxacin can push glucose up or down by affecting how your body handles sugar. If your glucose looks unexpectedly high or low, mention any medications or supplements you’re taking.
Calcium: More Than Bone Health
Normal serum calcium is 8.6 to 10.2 mg/dL. Your body stores most of its calcium in bone, but the small amount circulating in your blood is critical for nerve signaling, muscle contraction, heart rhythm, and blood clotting.
High calcium (hypercalcemia) is most commonly caused by overactive parathyroid glands or, less often, by certain cancers. Symptoms can include fatigue, frequent urination, and constipation. Low calcium can result from vitamin D deficiency, kidney problems, or low levels of parathyroid hormone. It may show up as muscle cramps or tingling in the fingers. One thing to note: the calcium on a BMP is “total calcium,” which includes calcium bound to a protein called albumin. If your albumin level is abnormally low (from liver disease or malnutrition, for example), your total calcium can look falsely low even when your actual usable calcium is fine.
Sodium, Potassium, Chloride, and CO2
These four electrolytes work together to regulate fluid balance, acidity, nerve impulses, and muscle function. Reading them as a group often tells a clearer story than looking at any one in isolation.
Sodium (136 to 145 mEq/L)
Sodium is the main electrolyte that controls how much water your body holds onto. A low reading (hyponatremia) is one of the most common electrolyte abnormalities and can result from drinking too much water, certain medications (especially some antidepressants and blood pressure drugs), or conditions that cause your body to retain water. Mild cases may cause no symptoms at all. Severe drops can lead to confusion, nausea, or headaches. High sodium usually points to dehydration, meaning your body has lost more water than salt.
Potassium (3.5 to 5.0 mEq/L)
Potassium is critical for your heartbeat. Both high and low values matter because either extreme can cause dangerous heart rhythm problems. Low potassium commonly results from vomiting, diarrhea, or diuretic (“water pill”) use. High potassium is often linked to kidney disease, since your kidneys are responsible for clearing excess potassium from the blood. Some blood pressure medications designed to protect the kidneys can also raise potassium as a side effect. If your potassium is even slightly outside the normal range, your doctor will likely want to recheck it.
Chloride (98 to 106 mEq/L)
Chloride tends to move in the same direction as sodium, so an abnormal chloride reading often has the same explanation. Where chloride becomes especially useful is in combination with the other electrolytes to calculate something called the anion gap (explained below).
CO2/Bicarbonate (23 to 28 mEq/L)
This value reflects the bicarbonate level in your blood, which is your body’s main acid buffer. A low CO2 can indicate that your blood is too acidic (metabolic acidosis), which may happen with uncontrolled diabetes, severe diarrhea, or kidney disease. A high CO2 can mean your blood is too alkaline, sometimes from prolonged vomiting or chronic lung conditions that cause you to retain carbon dioxide.
BUN and Creatinine: Your Kidney Check
These two values are waste products that your kidneys filter out of your blood. When your kidneys aren’t working efficiently, these numbers climb.
Normal BUN is 8 to 20 mg/dL. Normal creatinine is 0.5 to 1.1 mg/dL for women and 0.7 to 1.3 mg/dL for men (the difference exists because men generally have more muscle mass, and creatinine is a byproduct of muscle metabolism). Creatinine is the more reliable kidney marker of the two, because BUN can rise for reasons that have nothing to do with your kidneys, like eating a very high-protein diet or being dehydrated.
The ratio between BUN and creatinine adds useful context. In a typical situation, BUN runs at roughly 10 to 1 compared to creatinine. If that ratio climbs much higher, say 20 to 1 or above, it often suggests dehydration, heart failure, or something else reducing blood flow to the kidneys rather than actual kidney damage. A lower-than-expected ratio can point to liver disease or very low protein intake.
Your lab report may also include an eGFR (estimated glomerular filtration rate), which is calculated from your creatinine along with your age and sex. A normal eGFR is around 100. A sustained eGFR below 60 for three months or more is the definition of chronic kidney disease. This number is arguably the single most useful kidney reading on your panel because it translates your creatinine into a practical estimate of what percentage of normal kidney function you have.
The Anion Gap: A Hidden Calculation
Your lab may print an anion gap on your results even though it isn’t directly measured. It’s calculated from values already on your BMP using a simple formula: sodium minus (chloride plus bicarbonate). A normal anion gap is roughly 8 to 12 mEq/L.
A high anion gap means there’s extra acid in your blood that isn’t accounted for by the standard electrolytes. The most common causes are diabetic ketoacidosis (a serious complication of uncontrolled diabetes), kidney failure, and toxic ingestions. If your anion gap is elevated, your doctor will almost certainly investigate further. If it’s normal, you generally don’t need to think about it.
What Can Throw Off Your Results
Up to 43% of patients have at least one lab value influenced by a medication they’re taking, according to research published in Biochemia Medica. Antibiotics, particularly cephalosporins, are the most frequent offenders. They can falsely raise creatinine readings, making your kidneys look worse than they actually are. High-dose intravenous vitamin C can do the same thing and can also falsely raise glucose on certain testing methods. Contrast dye used for CT scans or other imaging can temporarily affect creatinine and calcium values.
Dehydration is another common confounder. It can artificially raise BUN, sodium, and glucose, making results look abnormal when the real issue is simply that you needed more water. If you fasted longer than instructed or didn’t drink enough fluids, mention it when reviewing results.
Reading the Results as a Whole
The real power of a BMP is in reading the values together rather than fixating on any single number. A high glucose paired with a high anion gap and low bicarbonate, for example, tells a very different story than a high glucose by itself. The first pattern suggests diabetic ketoacidosis, while the second might just mean you ate breakfast before a fasting test.
Similarly, a mildly elevated creatinine in someone who is muscular and well-hydrated means something different from the same creatinine in someone who is frail and dehydrated. Context matters enormously. One slightly out-of-range value on an otherwise normal panel is rarely cause for alarm. A cluster of abnormalities pointing in the same direction, like rising BUN, rising creatinine, and elevated potassium all suggesting kidney trouble, carries much more clinical weight.
When you look at your BMP results, start with the flagged values (most labs mark highs and lows with an “H” or “L”), check how far outside the range they fall, and consider whether anything obvious like fasting status, hydration, or a new medication could explain the result. That puts you in a much better position to have a productive conversation about what, if anything, needs to happen next.