Complete Blood Count

What this test actually measures

A blood count looks at the cells rather than the chemistry. Three populations, each answering a different question.

Red cells carry oxygen. The panel reports how many you have, how much hemoglobin they contain, and, most usefully, how big they are on average, which is the MCV.

White cells fight infection, and the differential breaks them into types, which is informative because different infections and conditions shift different subgroups.

Platelets handle clotting.

That is a genuinely broad screen of your blood as a tissue, and it is why this test is ordered more than almost any other. What it is not is a survey of your nutritional or hormonal status, which is where the misunderstanding usually starts.

The most useful number on it, and the biggest gap

Start with the number almost nobody reads, because it does more work than any other line on this report.

MCV, mean corpuscular volume, is the average size of your red blood cells. It turns a low hemoglobin from a fact into a direction.

Small cells point toward iron shortfall or a thalassaemia trait. Large cells point toward B12 or folate. Normal-sized cells with a low hemoglobin point somewhere else again, often toward chronic disease or blood loss.

So if your hemoglobin is low or low-normal, the next thing to look at is not another test, it is the number already printed next to it.

On the hemoglobin thresholds themselves, there is reassuring news. A 2024 analysis in The Lancet Haematology assembled healthy reference samples from eight international data sources and re-derived the anaemia cutoffs that had been set more than fifty years earlier, finding them broadly sound, with values diverging by sex from adolescence onward.

Now the gap, and it is the single most important thing on this page.

Your body protects circulating hemoglobin above almost everything else, drawing down stored iron for as long as it can to keep the number up. So iron stores can be completely empty while hemoglobin still reads normal.

That state has a name in the literature, iron deficiency without anaemia, and it is not fringe. A 2003 randomised trial in the BMJ tested iron supplementation specifically in non-anaemic women with unexplained fatigue, because researchers went looking in exactly that gap.

A blood count cannot see any of it. Ferritin can, and it is one extra line on the same order.

Test details

What is measured: red cells including hemoglobin, hematocrit and the red cell indices, white cells with a differential, and platelets.

Sample: blood draw.

Provider: Quest Diagnostics, ordered through Jess's practitioner dispensary.

Fasting: not required.

Turnaround: results typically within a few business days of the sample reaching the lab.

Order this test.

How the pricing works

I want to be straightforward about this, because lab pricing in the wellness industry frequently is not.

Jess takes no markup on the test itself. The lab cost is passed through exactly as it comes. What you pay is the test cost, the dispensary's service fee, the authorization fee, the collection fee where one applies, a flat handling fee for placing and managing the order, and the card processing cost. The handling fee is the part that is Jess's, and it is flat regardless of how expensive the test is.

That structure is deliberate. A percentage markup on labs creates an incentive to recommend expensive tests, and this way there is not one.

Because every blood test in one order shares a single draw fee, adding a second or third test to the same order costs considerably less than ordering them separately. The full lab menu shows what shares a draw with this one, and the order page itemises every fee before you pay.

Who this test is worth running for

It is a reasonable baseline for almost anyone, and most people have had one recently. If you have, the more useful move is often to read the one you already have properly rather than to repeat it.

Specifically worth running for unexplained fatigue, breathlessness on exertion, unusual bruising or bleeding, recurrent infections, or as the first step when working out why someone feels unwell.

The most important thing to know is what to order alongside it. If your question is tiredness, a blood count alone will very often come back normal and leave you no further forward. Ferritin with hs-CRP, B12 and folate, and a thyroid panel are what turn a blood count from a screen into an answer, and they all share one draw.

Ordering restrictions

The lab network cannot issue orders to residents of New York, New Jersey, Rhode Island, or Hawaii. New York, New Jersey, and Rhode Island prohibit direct-to-consumer lab testing outright, requiring a treating provider's signature on every requisition. Hawaii is excluded by the network. This is tied to where you live, not where the sample is collected, so it applies to kits as well as draws.

If you live in one of those four states, your doctor can order the same test.

What to do with the result

Read your MCV, not just your hemoglobin. Small cells, large cells and normal cells with a low count point in three different directions, and this is the number that tells you which.

If hemoglobin is genuinely low, that needs a cause found rather than a supplement started. Anaemia in an adult, particularly a man or a postmenopausal woman, warrants proper investigation.

If everything reads normal and you feel unwell, that is expected rather than contradictory. A blood count does not measure iron stores, vitamins, thyroid or blood sugar, and those are where the answer usually lives.

If white cells or platelets are abnormal, take that to a doctor rather than interpreting it here. Those results have a wide differential and they are not a wellness question.

Read the numbers alongside what they mean. The hemoglobin page covers the thresholds and the gap in detail.