Neutrophil-to-Lymphocyte Ratio (NLR)

What the NLR is and when it is used

The NLR is a simple ratio between two leukocyte populations in the complete blood count: neutrophils and lymphocytes. It was proposed by Zahorec in 2001, in the journal Bratislavské Lekárske Listy, as a rapid parameter of systemic inflammation and stress in critically ill patients.

The idea is that, in situations of stress and inflammation, neutrophils tend to rise and lymphocytes tend to fall, and the ratio amplifies this contrast. In a 2021 review article, the same author describes the NLR as a reflection of the relationship between the innate immune response, represented by neutrophils, and the adaptive response, represented by lymphocytes.

The NLR is used in studies in several areas, such as infection, sepsis, cardiovascular disease and cancer, almost always as a prognostic or monitoring marker rather than a diagnostic one. A similar ratio, which replaces neutrophils with platelets, is the platelet-to-lymphocyte ratio (PLR). Both use the same blood count that provides the red cell indices.

How to use the calculator: inputs and result

The calculator asks for two absolute counts from the same blood count:

• Neutrophils (absolute count). Example: 4500 or 4.5. The field accepts zero, but not negative values.
• Lymphocytes (absolute count), greater than zero. Example: 1500 or 1.5.

The fields have no fixed unit: the examples show the two common report formats, in cells/µL (4500) or in ×10³/µL, which is equivalent to ×10⁹/L (4.5). What matters is using the same unit in both fields.

Zero lymphocytes, negative values or counts that appear to be in different units (for example, 4500 and 1.5) produce an error message. The tool shows the NLR, unitless, with two decimal places, and the Zahorec (2021) range the value falls into, explained in the interpretation section.

A note reminds you that the NLR does not indicate the cause, cites the range of 0.78 to 3.53 found in healthy adults by Forget and colleagues (2017) and asks for both counts in the same unit. With the example values in the fields, the NLR is 3.00.

NLR formula and worked example

The NLR is the neutrophil count divided by the lymphocyte count:

NLR = Neutrophils ÷ Lymphocytes

Both counts must be in the same unit, and the result is unitless.

Didactic example (not an interpretation of a patient): 6,000 neutrophils/µL and 1,200 lymphocytes/µL.

1. NLR: 6,000 ÷ 1,200 = 5.00.
2. Zahorec range (2021): above 3.0, considered pathological in adults.

The same blood count reported in ×10³/µL (6.0 and 1.2) gives exactly the same result: 6.0 ÷ 1.2 = 5.00. What must not happen is mixing the two formats, such as 6,000 neutrophils and 1.2 lymphocytes, which would give 5,000.

A useful detail: since neutrophils and lymphocytes come from the same total leukocyte count, the ratio between the differential percentages (for example, 62% ÷ 25% = 2.48) equals the ratio between the absolute counts. The tool, however, asks for the absolute counts.

How to understand the NLR: reference values and cutoffs

The NLR has no universal cutoff, and the reading depends on the population and the condition studied. The most cited reference data come from two works:

• Forget and colleagues (BMC Research Notes, 2017) studied 413 healthy adults, with a median age of 38 years, and found a mean NLR of 1.65, with a range of 0.78 to 3.53.
• Zahorec, in the 2021 review, describes a normal range between 1 and 2, considers values above 3.0 and below 0.7 in adults pathological, and a gray zone between 2.3 and 3.0. According to the same review, most meta-analyses in solid tumors used a cutoff above 3.0.

The calculator follows Zahorec's ranges: below 0.7; from 1 to 2, normal; from 2.3 to 3.0, gray zone; above 3.0, pathological; and above 11, marked elevation, which the review associates with severe inflammation or disease. Values between 0.7 and 1 or between 2 and 2.3 appear as outside the normal range, without reaching pathological limits.

An isolated high NLR does not indicate a specific disease. Interpretation, with the clinical picture and other tests, is the responsibility of the professional.

Common errors, units and checklist

The most common error with the NLR is using different units in the two fields. Other points of attention:

• Mixed units: neutrophils in cells/µL and lymphocytes in ×10³/µL would give a result one thousand times larger; the calculator detects the obvious cases and shows an error.
• Different blood counts: both counts must come from the same sample, because the ratio changes quickly in acute situations.
• Band cells: check whether the laboratory reports total neutrophils or only segmented ones, and use the same criterion when comparing results over time.
• Very low lymphocytes: small differences in the denominator change the ratio a lot. With 300 lymphocytes/µL, 50 cells more or less change the NLR by 14% to 20%.
• Rounding: the range is decided by the unrounded value; 3.004 appears as 3.00 but is already past the limit of 3.0.

Checklist before using the result:

• Are both counts in the same unit?
• Are they from the same blood count?
• Is there medication use or an acute condition that alters leukocytes?
• Is the cutoff used for comparison that of the population and condition studied?

When the NLR may be inappropriate

The NLR is influenced by many factors besides the condition being assessed. In the 2021 review, Zahorec lists age, medications, chronic diseases such as coronary disease, stroke, diabetes and obesity, psychiatric diagnoses, solid organ cancer, anemia and stress.

For this reason, the result should be read with caution in situations such as:

• use of medications that alter leukocytes, such as corticosteroids and chemotherapy;
• hematological diseases that directly affect neutrophils or lymphocytes;
• populations different from the one studied: the values of Forget and colleagues apply to healthy, non-elderly adults;
• children, for whom the tool has no specific ranges.

Zahorec recommends following the NLR over time in acute and critical illness, observing absolute values and trends rather than an isolated result. In any case, the NLR complements, and does not replace, clinical assessment and other inflammatory markers.

NLR, PLR and other blood count markers

The NLR belongs to a group of ratios derived from the complete blood count used as inflammatory markers. The table compares the NLR with the PLR:

The two ratios share the denominator and therefore rise together when lymphocytes fall. To calculate the second one, use the PLR calculator with the same blood count. The red cell series of the same test can be checked with the red cell indices, and the marrow response to anemia with the reticulocyte production index.

Frequently asked questions about the neutrophil-to-lymphocyte ratio (NLR)

References

1. Zahorec R. Ratio of neutrophil to lymphocyte counts: rapid and simple parameter of systemic inflammation and stress in critically ill. Bratisl Lek Listy. 2001;102(1):5-14. View
2. Zahorec R. Neutrophil-to-lymphocyte ratio, past, present and future perspectives. Bratisl Lek Listy. 2021;122(7):474-88. doi:10.4149/BLL_2021_078. View
3. Forget P, Khalifa C, Defour JP, Latinne D, Van Pel MC, De Kock M. What is the normal value of the neutrophil-to-lymphocyte ratio? BMC Res Notes. 2017;10(1):12. doi:10.1186/s13104-016-2335-5. View