NLR (neutrophil/lymphocyte)

Neutrophils and lymphocytes are the two largest groups of white blood cells, and they respond in opposite ways to the same signal. Adrenaline and cortisol, the hormones of stress, loosen neutrophils from the vessel wall and release them from the bone marrow, and at the same time send lymphocytes out of the blood back to the lymph nodes. With an infection, an inflammation or an operation the same happens. One group goes up, the other down, and the ratio between the two amplifies that difference. That is the idea behind the NLR. Neutrophils are the fast, innate defence that responds to everything; lymphocytes are the specialists that need time and rest. A low ratio means the balance lies towards recovery and specialisation; a high one that your body is in the stress state. In a healthy adult at rest the two sit close together, and the ratio around 1 to 2. With a severe bacterial infection it can go above 10, and in someone who sleeps badly, is overtrained or smokes, it creeps slowly towards the top. Your report usually does not print the ratio; you calculate it yourself with the calculator on this page. The two studies that have published a reference interval come out at 0.78 to 3.53 and at 0.88 to 4.0, and where those overlap, between 0.88 and 3.53, lies the area that counts as healthy.

The NLR is one of the simplest ways to see how heavily your body is loaded. An athlete who trains too much without rest sees the neutrophils rise and the lymphocytes fall, and the ratio rises weeks before performance drops. Anyone who structurally sleeps too little or is under pressure for a long time sees the same. And because the ratio is fairly stable from day to day in the same person, a rise over a few measurements shows that something has changed, even when each of the two numbers separately still falls within the band. The second reason is inflammation. The smouldering inflammation of belly fat, smoking and little exercise lifts the neutrophils slightly and suppresses the lymphocytes slightly, and the ratio picks that up. An NLR that sits at the high end without an infection therefore goes with more cardiovascular disease and with a worse course of many illnesses, and it falls along when lifestyle changes. That makes it a usable measure to follow over the years, beside CRP, which measures the inflammation itself. The honest limitation is that the ratio does not say which of the two numbers moved. An NLR of 4 can come from a bacterium that lifted the neutrophils, from prednisone that suppressed the lymphocytes, or from a bad night that did both. That is why you always read it beside the two separate numbers and beside CRP, and why one result is a snapshot and the trend the real number.

A low NLR means the lymphocytes dominate, and that is usually favourable: the balance lies towards recovery. Below 0.88 the question is which side it comes from. More lymphocytes is usually a virus or the recovery phase after it, and then the ratio is temporarily low. Fewer neutrophils is a virus that has just passed, a medicine, or a naturally lower count, which is common in people with African or Middle Eastern ancestry; for them a low NLR is their usual state and not a finding. A high NLR means your body is in the stress state, and the question is why. Above 3.53 with fever and a high CRP it is a bacterial infection or an inflammation, and then the ratio falls with recovery. Without fever it is almost always load: a hard training session the day before, a bad night, a period of pressure, smoking, prednisone or belly fat. A ratio that stays at the high end over several measurements without an infection is the smouldering inflammation, and you read that beside your waist, your sleep and your CRP. The NLR belongs beside the neutrophils and lymphocytes themselves, because the ratio does not say which of the two moved, beside CRP, which says whether inflammation is running, and beside the PLR, which measures the same balance with platelets as the numerator and moves more slowly.