# Lymphocyte count: Your T cells, B cells and natural killer cells > Lymphocytes are the T cells, B cells and natural killer cells of your immune system. Check your count and see what low and high results mean. - Also called Absolute lymphocyte count, ALC and Lymphs (Absolute) - Often on a standard checkup - No fasting needed - Web page: https://picardo.health/guides/biomarkers/lymphocytes ## The short answer Lymphocytes are the T cells, B cells and natural killer cells of your immune system.[2] Labcorp’s range is 0.7 to 3.1 ×10³/µL.[1] Infections, stress and steroids can push the count out of range for a while, so a single result outside it is worth repeating before anything else.[2][3] - **A healthy range:** 1.0 to 3.1 ×10³/µL. Labcorp’s range starts at 0.7, but the usual definition of a low count is under 1.0.[1][2] - **If yours is low:** It’s often temporary, after an infection, stress or steroids.[2] If it stays low, find out why. In large studies, low counts went with higher death rates.[6][7] - **If yours is high:** A recent viral infection is one cause.[3] A count of 5.0 or more that lasts needs a closer look.[4] ## What is a normal lymphocyte count? Labcorp’s range is 0.7 to 3.1 ×10³/µL. Go by the absolute count, “Lymphs (Absolute)”, because the percentage has no range.[1] Other references put the normal adult range at 1.0 to 4.8, so both edges of Labcorp’s range are a gray zone:[2] | Result (×10³/µL) | What it means | | --- | --- | | Under 0.7 | Low: worth finding out why | | 0.7 to 0.9 | In Labcorp’s range, but low by the usual definition | | 1.0 to 3.1 | In the healthy range | | 3.2 to 4.9 | Above Labcorp’s range: repeat it in a few weeks | | 5.0 or more | Very high: needs a closer look | ### Low: worth finding out why **Range:** Under 0.7 ×10³/µL. This is low by any definition.[1][2] It’s often temporary, after a viral or bacterial infection, a serious illness or steroid treatment.[2] If it lasts, the causes a clinician will look for include HIV and other viral infections, undernutrition, heavy drinking, autoimmune disease, some cancers and medicines that suppress the immune system.[2] **How worried to be:** Not an emergency on its own. See a clinician in the next few weeks, or sooner if you keep getting infections or get unusual ones.[2] **What to do next:** 1. Repeat the count once you’ve recovered from any recent illness.[2] 2. If it stays low, ask about an HIV test. HIV is one of the most common causes.[2] 3. A clinician may also count your lymphocyte types and check your antibody levels.[2] [Test your blood count again, with an HIV test, $15.75](https://app.picardo.health/labs/order?tests=005009,083935&ref=guide-lymphocytes) ### In Labcorp’s range, but low by the usual definition **Range:** 0.7 to 0.9 ×10³/µL. Labcorp won’t flag this, but the usual definition of a low lymphocyte count is under 1.0.[1][2] A single result like this is often from a recent infection, stress or steroids, and passes.[2] **How worried to be:** Not a worry on its own. Worth a repeat to see whether it lasts. **What to do next:** 1. Repeat the count in a few weeks, once you’re well.[2] 2. If it stays under 1.0, raise it with a clinician. Large population studies link counts this low to higher death rates, though that doesn’t show the low count is the cause.[6][7] [Test your blood count again, $3.75](https://app.picardo.health/labs/order?tests=005009&ref=guide-lymphocytes) ### In the healthy range **Range:** 1.0 to 3.1 ×10³/µL. You have a normal number of lymphocytes.[1][2] **How worried to be:** Nothing to worry about. **What to do next:** 1. Keep this result to compare with future counts. Lymphocyte counts tend to fall with age, so a gradual drift down over the decades is expected.[7] ### Above Labcorp’s range: repeat it in a few weeks **Range:** 3.2 to 4.9 ×10³/µL. Labcorp’s upper limit is lower than many. Other references put it at 4.5 to 4.8, so a mild rise may be normal for you.[2][3] When the count is raised, causes include viral infections, whooping cough, allergic-type reactions and not having a working spleen.[3] **How worried to be:** Not urgent. A repeat once any infection has passed is the first step.[3] **What to do next:** 1. Repeat the count in a few weeks.[3] 2. If it stays up, a clinician can look at the cells under a microscope: cells of varied shapes and sizes point to a reaction to something, while cells that all look alike raise the question of a clone.[3] [Test your blood count again, $3.75](https://app.picardo.health/labs/order?tests=005009&ref=guide-lymphocytes) ### Very high: needs a closer look **Range:** 5.0 ×10³/µL or higher. This can still be a reaction to an infection,[3] but it’s also the level where chronic lymphocytic leukemia (CLL) becomes possible. CLL is usually diagnosed when at least 5.0 ×10³/µL of B cells from a single clone stay in the blood for 3 months or more, confirmed by a test called flow cytometry.[4] A blood count alone can’t diagnose it. **How worried to be:** See a clinician in the next few weeks. Go sooner if you have night sweats, weight loss, fevers or swollen glands, or your other counts are off.[3] **What to do next:** 1. Ask for a repeat count and a look at the cells under a microscope.[3] 2. If it stays high, ask whether you need flow cytometry, which shows whether the cells come from one clone.[3][4] 3. If there’s a clone but it’s below the CLL threshold, it’s called monoclonal B-cell lymphocytosis (MBL). Each year, about 1% to 2% of people with it go on to need treatment for CLL.[4] [Test your blood count again, $3.75](https://app.picardo.health/labs/order?tests=005009&ref=guide-lymphocytes) ## What is a lymphocyte count? > Only a small share of your lymphocytes are in your blood at any moment. Most live in your lymph nodes, spleen and other tissues, so the count is a snapshot of the traffic, not the whole army.[2] About three in four blood lymphocytes are T cells, one in five are B cells and the rest are natural killer cells.[2] Together they make up only 20% to 40% of your white cells, so a low lymphocyte count can sit inside a normal total white count.[2] ## What causes a low lymphocyte count? Often it’s something temporary:[2] - A viral or bacterial infection, including COVID-19 and the flu - The stress of a serious illness - Steroid medicines When it lasts, the causes include:[2] - HIV, one of the most common causes - Undernutrition, heavy drinking or low zinc - Autoimmune disease, such as lupus or rheumatoid arthritis - Lymphoma and sarcoidosis - Chemotherapy, radiation and medicines that suppress the immune system - Rarely, an inherited immune disorder ## Does a low lymphocyte count matter? Over the long run, it can. In a Danish study of more than 108,000 adults followed for about 9 years, those with counts under 1.1 ×10³/µL had about 1.6 times the death rate of those with counts of 1.1 to 3.7, after allowing for smoking, alcohol, weight, diabetes and other factors.[7] Deaths from heart disease, cancer and infections were all higher.[7] A US survey of more than 31,000 adults found the same pattern, with higher risk at 1.5 or less and higher still at 1.0 or less.[6] These are observational links, and a low count may be a sign of illness rather than its cause. But a count that stays low is a reason to look for one.[2] ## What causes a high lymphocyte count? - A viral infection[3] - Whooping cough, and some other infections such as syphilis[3] - Allergic-type (hypersensitivity) reactions[3] - Not having a working spleen[3] - A leukemia or lymphoma, such as chronic lymphocytic leukemia (CLL)[3] A high count is more likely to be harmless in children than in adults.[3] ## Who should get a lymphocyte count? A lymphocyte count comes with every complete blood count with a differential, so you may already have one. It’s worth a look if any of these apply to you: - You have HIV, or might have been exposed to it.[2] - You take steroids or other medicines that suppress the immune system, or have had chemotherapy or radiation.[2] - You have swollen glands, night sweats, fevers or weight loss you can’t explain.[3] - A past count was high or low and you want to see whether it has moved. ## How to get a lymphocyte count test, and what it costs It comes from the complete blood count, which costs $3.75 through Picardo. - [Complete blood count, $3.75](https://app.picardo.health/labs/order?tests=005009&ref=guide-lymphocytes). The test this number comes from. Labcorp 005009, no fasting needed. Every order comes with: - Results in 2 to 3 days, in the app - Physician follow-up if you want one - Free Labcorp draw, or $75 at home - No other fees. HSA and FSA eligible. It’s also part of the [Base Core Annual – Men](https://picardo.health/labs/panels/base-core-men), [Base Core Annual – Women](https://picardo.health/labs/panels/base-core-women), [Heart Health](https://picardo.health/labs/panels/heart-health), [Brain Health Screening](https://picardo.health/labs/panels/brain-health), [Pregnancy](https://picardo.health/labs/panels/pregnancy), [Postpartum](https://picardo.health/labs/panels/postpartum), [Fertility](https://picardo.health/labs/panels/fertility), [Thyroid & Autoimmunity](https://picardo.health/labs/panels/thyroid-autoimmunity) and [Celiac / GI](https://picardo.health/labs/panels/celiac-gi) panels, if you’d rather test more at once. Already have a result? [Ask Picardo about it](https://app.picardo.health/auth). ## Questions people ask ### Can stress lower your lymphocyte count? Yes. Stress responses, such as a serious illness, can lower it for a while, and so can steroid medicines.[2] A repeat once things have settled shows whether it was temporary. ### Could a high lymphocyte count be leukemia? It could, which is why a count that stays at 5.0 or more gets a closer look.[4] But small clones of B cells are common with age. In a Minnesota study that screened more than 10,000 adults aged 40 or older, 17% had one, rising from 4% in their 40s to 42% at 90 and over. Most clones were tiny: people with them lived as long as people without, and as a group, people with a clone developed a blood cancer at about 0.5% a year.[5] ### What is the neutrophil-to-lymphocyte ratio? Your neutrophil count divided by your lymphocyte count, used as a marker of inflammation. In a Dutch study of about 8,700 older adults, those with higher ratios had higher death rates, even after allowing for age, smoking, diabetes and past heart disease or cancer.[8] It isn’t a diagnosis on its own. ### Do lymphocytes go down with age? Yes, on average.[7] In a large Danish study, people with low counts were typically about 10 years older than the rest, with a median age of 68 against 58.[7] ### Does a low lymphocyte count mean a weak immune system? A brief dip after an illness doesn’t. A count that stays low can, and recurring or unusual infections are the main sign. A clinician can then check which types of lymphocytes are low and how well you make antibodies.[2] ## Often checked alongside - [White blood cell count](https://picardo.health/guides/biomarkers/white-blood-cells.md): Cells that fight infection - [Neutrophil count](https://picardo.health/guides/biomarkers/neutrophils.md): White cells that fight bacterial infections - [Platelet count](https://picardo.health/guides/biomarkers/platelets.md): Cells that help blood clot - [Hemoglobin](https://picardo.health/guides/biomarkers/hemoglobin.md): Carries oxygen; low levels mean anemia ## Test details - **Labcorp test:** Complete Blood Count (CBC) With Differential, Reflex to Peripheral Smear Review, 005009 - **LOINC:** 731-0 - **Sample:** Blood - **Fasting:** Not needed - **Typical lab range:** 0.7 to 3.1 ×10³/µL - **Units:** ×10³/µL, which Labcorp prints as x10E3/uL. It’s the same number as ×10⁹/L. ## Sources 1. Labcorp. CBC with differential/platelet, test 005009: sample patient reports (female, age 46; reported September 15, 2026). Burlington, NC: Labcorp; 2026. Accessed October 28, 2026. https://files.labcorp.com/testmenu-d8/sample_reports/005009.pdf 2. Dale DC. Lymphocytopenia. Merck Manual Professional Edition. Reviewed February 2025; updated April 2026. Accessed October 28, 2026. https://www.merckmanuals.com/professional/hematology-and-oncology/leukopenias/lymphocytopenia 3. Riley LK, Rupert J. Evaluation of patients with leukocytosis. Am Fam Physician. 2015;92(11):1004–1011. https://pubmed.ncbi.nlm.nih.gov/26760415/ 4. Hallek M, Cheson BD, Catovsky D, et al. iwCLL guidelines for diagnosis, indications for treatment, response assessment, and supportive management of CLL. Blood. 2018;131(25):2745–2760. https://doi.org/10.1182/blood-2017-09-806398 5. Slager SL, Parikh SA, Achenbach SJ, et al. Progression and survival of MBL: a screening study of 10 139 individuals. Blood. 2022;140(15):1702–1709. https://doi.org/10.1182/blood.2022016279 6. Zidar DA, Al-Kindi SG, Liu Y, et al. Association of lymphopenia with risk of mortality among adults in the US general population. JAMA Netw Open. 2019;2(12):e1916526. https://doi.org/10.1001/jamanetworkopen.2019.16526 7. Warny M, Helby J, Nordestgaard BG, Birgens H, Bojesen SE. Incidental lymphopenia and mortality: a prospective cohort study. CMAJ. 2020;192(2):E25–E33. https://doi.org/10.1503/cmaj.191024 8. Fest J, Ruiter TR, Groot Koerkamp B, et al. The neutrophil-to-lymphocyte ratio is associated with mortality in the general population: the Rotterdam Study. Eur J Epidemiol. 2019;34(5):463–470. https://doi.org/10.1007/s10654-018-0472-y Updated 2026-10-28. This is general health information, not medical advice: talk to your clinician about your results and before changing any treatment.