Home › Biomarkers › Reticulocytes
Reticulocytes are young red blood cells made by your bone marrow. A level that is too low or too high can point to anaemia or to a condition of the bone marrow, liver or kidneys.[1]
On this page you can read what reticulocytes are, what the guidelines say about a low or high level, what affects your level and which other values are best read alongside it.
Also known as: retic count, reticulocyte percentage, reticulocyte index, corrected reticulocytes, reticulocyte production index (RPI). At the lab: RETI.
Reticulocytes are red blood cells that are still developing. Your body makes them in your bone marrow. They then move into your blood, where they mature into red blood cells within one to two days.[1]
Your bone marrow keeps making new red blood cells, as many as your body needs. A reticulocyte count checks whether your bone marrow is making enough new cells as old cells die off.[1]
For the test, blood is taken from a vein in your arm. You don't need to do anything special to prepare.[1]
Red blood cells carry oxygen from your lungs to every cell in your body. If you have too few, your tissues may not get enough oxygen. If you have too many, you may be at risk of blood clots or other health problems.[1]
Your doctor may order this test if other blood tests, such as hemoglobin or hematocrit, show that your red blood cells are not normal. The test also helps to track how a level changes during treatment for anaemia.[1]
Symptoms that fit with anaemia can also be a reason. Think of shortness of breath, weakness or tiredness, headache, dizziness, or a problem with the speed or rhythm of your heartbeat.[1]
Labplusarts, the lab BioProfile works with, uses a reference range for reticulocytes of 20 to 100 10^9/l. The lab calls a level within these limits normal.[2]
| Value | What it can mean | Who it is for |
|---|---|---|
| Higher than normal[1] | Can point to anaemia in which red blood cells are broken down faster than the bone marrow can replace them | Everyone who is tested |
| Higher than normal[1] | Can point to new or ongoing blood loss, where your body makes extra red blood cells | Everyone who is tested |
| Higher than normal[1] | Can be part of being pregnant, without there being a condition | People who are pregnant |
| Briefly higher than normal[1] | Can be part of adjusting to less oxygen at high altitude | People who have just travelled somewhere at high altitude |
| Lower than normal[1] | Can point to iron deficiency, too little vitamin B12 or folic acid, or a condition of the bone marrow, kidneys or liver | Everyone who is tested |
| Higher or lower than normal[1] | Can be caused by some medicines | People who take medicines |
Source: MedlinePlus, a public resource of the U.S. National Library of Medicine. The source gives no cut-off values, only what a higher or lower than normal level can mean.[1]
A lower than normal level can point to iron deficiency, the most common form of anaemia. It can also point to anaemia caused by too little vitamin B12 or folic acid, either from your diet or because your body does not absorb them well. It can also point to bone marrow that is not making enough blood cells, or to a kidney condition or scar tissue in the liver. Your doctor also looks at your symptoms, your medical history and your other blood values.[1]
A higher than normal level can point to anaemia in which red blood cells are broken down faster than your bone marrow can replace them. It can also point to new or ongoing blood loss, where your body makes a lot of extra red blood cells to make up for the loss. An abnormal level does not always mean there is a condition.[1]
BioProfile is working on its own zones for each value, from risk to optimal. A doctor reviews those zones before they appear in your result.
If you are pregnant, your reticulocyte level can be higher without this pointing to a condition.[1]
If you go somewhere at high altitude, your level can rise for a while. Once your body has adjusted to the lower amount of oxygen, your level should return to normal.[1]
Some medicines can raise or lower your reticulocyte level.[1]
If you get too little iron, vitamin B12 or folic acid from your diet, or your body does not absorb them well, your level can be lower.[1]
Reticulocytes are included in BioProfile 87, 121 and 150.[3]
The BioProfile editorial team wrote this page on 10 October 2026 from the sources below, which we read on 10 October 2026. Every number on this page appears in one of those sources, with that source's number next to it. An expert has yet to check this page; after that check, the expert's name and the date of the check will appear at the top. This page offers explanation, not a diagnosis. Discuss a value outside the range with your GP.
