September 2026

Reading ng/mL and Other Units on Your Lab Report

By Your Health Magazine Health Information Team

You open your lab report and see a result such as “24 ng/mL.” The number looks straightforward, but what is ng mL, and is 24 high, low, or normal? The unit is an essential part of the answer. A number without its unit—and without the test’s reference range—cannot tell you much about your health.

What Is ng/mL?

Ng/mL means nanograms per milliliter. It is a unit of concentration that describes how much of a substance is present in a specific volume of fluid, usually blood, serum, plasma, or urine.

“ng” means nanogram. One nanogram is one-billionth of a gram.
“mL” means milliliter. One milliliter is one-thousandth of a liter.
The slash means “per,” so ng/mL is read as “nanograms per milliliter.”

If a report lists a result of 24 ng/mL, the laboratory detected 24 nanograms of the measured substance in each milliliter of the tested sample. That may sound extremely small, but modern laboratory instruments can measure substances present in tiny concentrations.

Ng/mL is a mass-concentration unit. It tells you the mass of a particular substance relative to the volume of the sample. It does not describe the total amount of that substance in your entire body.

Which Tests May Use ng/mL?

Laboratories may use ng/mL for substances found in relatively small amounts. Depending on the laboratory and testing method, examples can include vitamin D, ferritin, prostate-specific antigen, certain hormones, and some medication levels.

The unit alone does not identify the test or reveal whether the result is healthy. A vitamin level and a medication level might both be reported in ng/mL, yet they have completely different reference or target ranges. Always match the number and unit to the exact test name.

For an additional plain-language explanation, see this guide to understanding ng/mL and what it can mean for your health.

How to Read a Result Reported in ng/mL

Start by reviewing the full row on the lab report rather than focusing only on the number. Most reports include several pieces of information:

The name of the substance or test
Your numerical result
The measurement unit, such as ng/mL
The laboratory’s reference interval or target range
A flag such as high, low, abnormal, or critical
Information about the specimen or collection time, when relevant

Compare your result only with the reference interval printed beside that result. Laboratories can use different instruments, testing methods, sample types, and reference populations. As a result, the expected range at one laboratory may differ from the range used elsewhere.

A result just outside a reference interval does not automatically establish that you have a disease. Healthy people can occasionally have results outside a listed range, while a result inside the range does not always rule out a health problem. Clinicians interpret laboratory findings alongside symptoms, medical history, physical examination, medications, and other test results.

How ng/mL Compares With Other Units

Lab reports use different units because substances occur at different concentrations and may be measured by mass, number of particles, electrical activity, or biological activity. Common units include:

pg/mL: picograms per milliliter; a picogram is smaller than a nanogram.
mcg/mL or µg/mL: micrograms per milliliter; one microgram equals 1,000 nanograms.
mg/dL: milligrams per deciliter, often used for substances present in larger concentrations.
mmol/L or nmol/L: millimoles or nanomoles per liter, which describe the number of molecular particles rather than their mass.
IU/L or IU/mL: international units per liter or milliliter, which describe biological activity defined for a particular substance.

For straightforward mass concentration, 1 ng/mL equals 1 microgram per liter, written as 1 µg/L. However, you should not assume that every unit can be converted by simply moving a decimal point.

Converting between ng/mL and a molar unit such as nmol/L requires the molecular weight of the specific substance. The correct conversion factor for vitamin D, for example, is not automatically correct for a hormone or medication. International units also cannot be converted to mass with one universal formula because an IU represents a substance-specific level of biological activity.

Why Two Reports May Show Different Numbers

A test may appear different when another laboratory uses a different unit. A result written in ng/mL can have a much larger or smaller numerical appearance after conversion, even though the actual concentration has not changed.

Testing conditions may also affect certain results. Depending on the test, relevant factors can include the time of day, fasting status, recent exercise, illness, pregnancy, medication use, supplement use, and how long it has been since a medication dose. For monitored medications, collection timing may be especially important because the amount in the blood can rise and fall between doses.

If your clinician is following a trend, using the same laboratory when practical can make comparisons easier. When results come from different facilities, confirm that the test name, sample type, units, and reference ranges match before drawing conclusions.

Common Lab-Reading Mistakes

Ignoring the unit and comparing only the numerical value
Using a reference range found online instead of the range on the report
Comparing results from different tests because both use ng/mL
Confusing ng with mg, mcg, or pg
Converting ng/mL to nmol/L without an analyte-specific conversion factor
Assuming every flagged result represents a medical emergency
Changing a medication or supplement based on one result without professional guidance

Symbols matter as well. A result shown as “less than” or “greater than” a value may indicate that the concentration falls beyond the laboratory’s reporting or measurement boundary. Ask the ordering clinician what that wording means for the specific test.

When to Seek Care

Contact the healthcare professional who ordered the test if a result is flagged, differs significantly from an earlier result, does not fit your symptoms, or relates to a medication that requires blood-level monitoring. A primary care clinician can interpret many routine results, while an endocrinologist, hematologist, urologist, pharmacist, or another specialist may help with particular tests.

Do not stop or change a prescription medication or begin high-dose supplements solely because of an online range or unit conversion. Seek urgent medical help for severe symptoms such as chest pain, major breathing difficulty, fainting, a seizure, sudden confusion, or profound weakness, regardless of what a patient portal displays.

The Bottom Line

When someone asks, “What is ng mL?” the short answer is nanograms per milliliter—a measurement of a very small mass of a substance in a milliliter of fluid. To understand what your result means, read the test name, number, unit, reference interval, and any collection instructions together. For reliable background information about conditions and medical testing, you can also explore MedlinePlus health topics. Your healthcare professional can then place the result in the context of your symptoms, health history, and other findings.