How to track your hemoglobin and CBC over time

The complete blood count, or CBC, is the most common blood test there is. It comes with physicals, hospital visits, pregnancy checks, and almost every new prescription that needs monitoring. Most people have dozens of them, from many labs, and have never looked at more than the flags. A CBC is a good test to track because most of it is stable within a person. When something moves, a run of results can show whether it is new, how fast it is moving, and what else changed at the same time.

What the CBC measures

A CBC counts and measures the three kinds of cells in your blood. A full report, with the differential, often runs to a dozen lines or more.

Red cells:

• Hemoglobin: the oxygen-carrying protein, per volume of blood. This is the number used to define anemia.
• Hematocrit: the share of blood volume taken up by red cells.
• RBC: the red cell count.
• MCV: the average size of a red cell.
• MCH and MCHC: the average amount and concentration of hemoglobin in each cell.
• RDW: how much red cells vary in size.

White cells:

• WBC: the total white cell count.
• The differential: the breakdown into neutrophils, lymphocytes, monocytes, eosinophils, and basophils. Each appears twice, as a percentage of the total and as an absolute count.

Platelets: the platelet count, often with MPV, their average size.

Not every line is worth a chart. The ones that tell the clearest story over time are:

• Hemoglobin, for anemia and for anything that raises red cells.
• MCV, which shifts when iron, B12, or folate run short.
• WBC and the absolute neutrophil count, which many medications and infections move.
• Platelets.

Hematocrit and RBC usually move with hemoglobin, so they add little once hemoglobin is charted. The percentages in the differential can move just because another cell type changed, so chart the absolute counts instead. The neutrophil-to-lymphocyte ratio calculator turns two lines of the differential into a single, nonspecific marker of inflammation.

The numbers on the report

Units

Hemoglobin is reported in g/dL in the United States, in g/L in much of the world, and in mmol/L in a few countries. g/L is g/dL times 10. The WHO’s 2024 guideline on hemoglobin cutoffs gives 10 g/L as 0.62 mmol/L.

Counts come in many spellings for the same unit. For white cells and platelets, K/µL, 10^3/µL, thou/µL, and 10^9/L are all the same number: a WBC of 6.2 K/µL is 6.2 × 10^9/L. Some labs report the differential in cells/µL, so 3,100 cells/µL is 3.1 K/µL. For red cells, M/µL and 10^12/L are the same. Hematocrit is usually a percentage, but some labs report it as a fraction, so 42 percent and 0.42 L/L are the same result.

The range depends on who you are

Hemoglobin cutoffs differ by sex, age, and pregnancy. The WHO’s 2024 guideline sets these for anemia, based on the 5th percentile of healthy people:

Your lab’s range may differ, and its flag may be set from its own population. The guideline also adjusts for a few things that raise hemoglobin without any change in health:

• Altitude. Living higher raises hemoglobin. WHO subtracts 4 g/L for 500 to 999 m above sea level, 8 for 1,000 to 1,499 m, 11 for 1,500 to 1,999 m, and 14 for 2,000 to 2,499 m, with larger adjustments higher up. Someone who moves from the coast to a mountain city can see a step in their history from that alone.
• Smoking. WHO subtracts 3 g/L for fewer than 10 cigarettes a day, 5 for 10 to 19, and 6 for more. A rise in hemoglobin while smoking, or a dip after quitting, may be this.
• Ancestry. WHO notes that a mean hemoglobin about 10 g/L lower has been reported in Black individuals than in White individuals, but it does not recommend adjusting for it, citing insufficient evidence and the difficulty of applying it.

The guideline also notes that fingerstick results vary from venous ones by an amount that is not settled, so a hemoglobin from a fingerstick at a blood drive and one from a lab draw are not quite comparable.

Neutrophils and the Duffy-null phenotype

Many healthy people of African and Middle Eastern ancestry have a lower neutrophil count with no added risk of infection. It is tied to a variant of the Duffy blood group gene and is now called Duffy-null associated neutrophil count, or DANC. A 2026 study in JCO Global Oncology describes it as formerly known as benign ethnic neutropenia, and notes that it does not represent a true neutropenic state.

The numbers matter. A 2023 JAMA research letter notes that the Duffy-null phenotype is found in 66.7 percent of people in the U.S. who identify as Black. Its authors proposed a neutrophil range of 1,210 to 5,390 cells/µL for Duffy-null individuals, against their hospital’s standard range of 1,920 to 7,600 cells/µL. The median was 2,820 for Duffy-null individuals and 4,750 for the reference group.

For tracking, this means a neutrophil count that is always flagged low, and always about the same, may be your normal rather than a problem. A 2024 study in JAMA Network Open found that many cancer trials exclude, and many chemotherapy regimens reduce doses for, counts in this range, so if a low count has ever affected your treatment, a long history of stable values, and a Duffy test if your clinician orders one, are worth having on hand. Why are lab reference ranges different? covers how ranges are set and why one range rarely fits everyone.

How often it is tested

A CBC has no single schedule. It shows up:

• At routine visits, in many practices.
• To investigate symptoms such as tiredness, bruising, or frequent infections.
• Before and during treatment with medications that can affect blood counts, including chemotherapy, some immune-suppressing drugs, and testosterone.
• In pregnancy, usually more than once.
• After an abnormal result, often within weeks.
• During treatment for anemia. The British Society of Gastroenterology guideline on iron deficiency anemia says a hemoglobin rise of at least 10 g/L within two weeks of starting iron strongly suggests iron deficiency was the cause.

Because a CBC is drawn so often, most people already have a long history. The work is gathering it. How to get all of your medical records covers requesting older results from clinics and hospitals.

What counts as a real change

Some CBC values barely move within a person, and some move a lot. In a study of 30 healthy adults sampled weekly for 10 weeks, part of the European Biological Variation Study, researchers measured how much each value varied on its own and how far apart two results had to be before the change was likely to be real (the reference change value):

WBC and neutrophils show a range because the study found more variation in women than in men and reported the two separately.

In practice:

• A hemoglobin of 13.8 followed by 13.2 g/dL is within ordinary noise. A fall from 13.8 to 12.5 is past it.
• MCV is very stable. A move from 88 to 93 fL is well beyond noise and worth noticing even though both values are inside most labs’ ranges.
• WBC and neutrophils swing a lot. A WBC of 5.5 followed by 6.5 is not news. Look at the absolute neutrophil count over several draws rather than one.
• Platelets moving from 250 to 210 is within noise. A steady slide over several draws is more telling than one low value.

For hemoglobin, MCV, and WBC, the study also found high individuality: each person’s normal sits in a narrow part of the population range. A result inside the lab’s range can still be a real change for you.

Things that move the CBC

Hemoglobin and hematocrit up

• Dehydration. Less plasma concentrates the blood, so hemoglobin and hematocrit both read higher. A draw after an illness with vomiting or a day without fluids may not match your usual.
• Altitude and smoking, as above.
• Testosterone therapy. Testosterone raises red cell production, and hematocrit is checked on a schedule during treatment. How to track your testosterone over time covers that schedule and the level at which guidelines advise stopping.

Hemoglobin down

• Blood donation. In a randomized trial of blood donors, hemoglobin fell by about 1.3 to 1.4 g/dL after one whole-blood donation. Without iron, recovering 80 percent of that drop took a mean of 78 days in donors with higher iron stores and 158 days in those with low stores. With a low-dose iron pill, it took about a month. A frequent donor’s history can show a sawtooth.
• Menstruation and heavy periods. Your cycle shows up in your labs covers how hemoglobin differs with the timing of the draw.
• Pregnancy. Blood volume expands, which dilutes hemoglobin. Data the WHO guideline cites from the INTERGROWTH-21st project found median hemoglobin highest at 14 weeks (121.4 g/L), lowest at 31 to 32 weeks (114.6 g/L), and rising again to 118.7 g/L at 40 weeks.
• Iron deficiency. The BSG guideline notes that iron deficiency lowers MCH and MCV, and that MCH may be the more sensitive of the two. Hemoglobin usually falls later. How to track your ferritin over time covers the iron side.
• B12 or folate deficiency. These cause anemia with large red cells, a rising MCV, and sometimes lower white cell and platelet counts. How to track your vitamin B12 over time covers that test. The BSG guideline warns that a low MCV and MCH are less reliable signs of iron deficiency when B12 or folate deficiency is also present.
• Kidney disease. Damaged kidneys make less erythropoietin, the hormone that tells the bone marrow to make red cells. The NIDDK notes that anemia is less common early in kidney disease and more common as kidney function declines. How to track your eGFR over time covers that side. If your hemoglobin and eGFR have been falling together, chart them together.

White cells

• Infection and inflammation often raise the WBC, mostly through neutrophils. A WBC drawn during or just after an illness may not match your usual.
• Steroids. In a study of 80 patients taking prednisone, the WBC passed 20,000/mm³ in some patients as early as the first day, peaked within two weeks in most, and stayed above the pretreatment level for as long as treatment continued. The rise was mostly neutrophils, with fewer lymphocytes and eosinophils. A high WBC during a course of prednisone may be the drug, not an infection.
• Chemotherapy and some other medications lower white cells, and often platelets and hemoglobin too. Treatment teams set their own thresholds and testing schedule.

MCV

MCV is one of the steadiest numbers on the report, so a drift is worth noticing. It tends to fall with iron deficiency and rise with B12 or folate deficiency. The BSG guideline notes that thalassemia also lowers it, often out of proportion to any anemia. Because of the mixed-deficiency problem above, a normal MCV does not rule out a deficiency.

Did the medication actually do anything? covers reading a before-and-after fairly, whether the treatment was iron, B12, or a drug that affects blood counts.

What to record with each result

For each CBC, keep:

Names vary. Hemoglobin appears as Hgb, Hb, and Haemoglobin, platelets as PLT and Platelet Count, and WBC as White Blood Cell Count and Leukocytes. The absolute neutrophil count appears as ANC, Absolute Neutrophils, Neutrophils (Absolute), and Neutrophils #. Keep the percentage and the absolute count as separate tests, and pick one name for each.

Charting it

A few choices make a CBC chart honest:

• Chart a few values, not twenty. Hemoglobin, MCV, WBC, absolute neutrophils, and platelets cover most questions.
• Use your own baseline as well as the lab range. A hemoglobin that has sat at 14.5 for years and is now 12.8 is a change, even though both are in range.
• Mark donations, pregnancies, steroid courses, and moves to a new altitude, so steps in the line have their explanation beside them.
• Put ferritin, B12, or eGFR on the same timeline when you are looking for the cause of a low hemoglobin.
• Space points by date. Weekly counts during chemotherapy and a yearly physical should not look evenly spaced.
• Use a table view for the whole panel. For a full CBC across several dates, a side-by-side table is easier to read than twenty charts.

How to track your lab results over time has the general method for any test.

Tracking your CBC in HealthViewer

HealthViewer is a lab results tracker that runs on your own computer. It imports blood counts from lab report PDFs, MyChart downloads, and direct connections to your health system, and files common names under one test: Hgb and Haemoglobin as Hemoglobin, Hct as Hematocrit, PLT and Platelet Count as Platelets, and White Blood Cell Count and Leukocytes as WBC. MCV, MCH, MCHC, and RDW are recognized, including results your health system sends under their standard codes. Names for the absolute neutrophil count, such as Absolute Neutrophils and Neutrophils (Absolute), file under their own test, apart from the neutrophil percentage.

Units are converted so results share one chart. Hemoglobin in g/dL, g/L, and mmol/L converts between all three, and counts in K/µL, 10^3/µL, and 10^9/L are treated as the same unit, with cells/µL converted to match. A hematocrit reported as a fraction such as 0.42 L/L is not converted to a percentage. If your history mixes the two, the fraction results are listed under the chart rather than plotted on the wrong scale. If one of your labs uses a name HealthViewer does not recognize, combine it with Merge… in the Test Catalog.

In Trends, the Blood tag pulls the CBC’s red cell, white cell, and platelet values together, and the Complete Blood Count panel filter shows the tests from your CBC panels. The tag holds the differential’s percentages, so add the absolute counts to it in the Test Catalog if you chart those. The Cross-Date view puts a whole panel side by side, one column per draw. The overlay view puts hemoglobin and ferritin, or hematocrit and testosterone, on one chart.

Enter iron, B12, testosterone, or a steroid course in Medications, and medication markers show where each started and stopped. Add a journal entry for a blood donation, an illness, or a move, then turn on Show journal to see it on the chart. If your clinician uses a different range for you, for example a Duffy-null neutrophil range, set it as a custom range in the Test Catalog, and the chart shades your range instead of the lab’s.

Everything stays in an encrypted file on your computer, with no account and no cloud service. Getting Started walks through the first import.

This post is general information, not medical advice. Talk to your clinician about what your blood count means for you and before changing any treatment.