Is my red blood cell count low?
Yes, if it’s under your lab’s range, often 4.5 for men and 3.8 for women. But the count can’t tell you why it’s low. Another line on the same sheet gives a clue.
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Is my RBC count low?
It is if it sits below the range printed next to it. Two NHS labs both start their range at 4.5 for men and 3.8 for women. Their top ends differ, so read your own sheet.
The unit, x10¹²/L, means trillions of red cells in each litre of blood.
- Below 4.5 x10¹²/LBelow range. Ask your GP what’s next.
- 4.5 up to 6 x10¹²/LIn range at both labs.
- Above 6 up to 6.5 x10¹²/LAbove one lab’s range, in the other’s.
- Above 6.5 x10¹²/LAbove both labs’ ranges.
Sources: Severn Pathology (North Bristol NHS); Gloucestershire Hospitals NHS
- Below 3.8 x10¹²/LBelow range. Ask your GP what’s next.
- 3.8 up to 5.3 x10¹²/LIn range at both labs.
- Above 5.3 up to 5.8 x10¹²/LAbove one lab’s range, in the other’s.
- Above 5.8 x10¹²/LAbove both labs’ ranges.
Sources: Severn Pathology (North Bristol NHS); Gloucestershire Hospitals NHS
Think of red cells as delivery vans. Each one carries haemoglobin, which takes oxygen from your lungs to every cell.
Fewer vans can mean less oxygen gets delivered. That’s why a low count can come with tiredness, breathlessness, headaches, dizziness or pale skin.
Your next move: check your range, then look at the lines just below the count.
What causes a low red blood cell count?
Anaemia means your blood has too few red cells or too little haemoglobin.
| Cause | Examples |
|---|---|
| Too little iron | The most common type of anaemia. Heavy periods and pregnancy are very common causes. |
| Blood loss | Bleeding from the stomach or gut, such as from ulcers, piles or painkillers like ibuprofen. |
| Too little B12 or folate | For B12, most often pernicious anaemia, where the immune system stops you absorbing it. |
| Other conditions | Pregnancy, kidney failure, alcohol use disorder or a poor diet. |
| Blood cancers | Leukaemia, or myeloma, a cancer of the bone marrow. |
Sources: NHS: iron deficiency anaemia; NHS: B12 or folate deficiency anaemia; MedlinePlus
Lack of iron is the most common type of anaemia. Cancers of the bowel or stomach can cause it, but the NHS says this is less common.
Vegan? A lack of B12 from food is uncommon, but it can happen. The risk is if you don’t take a B12 supplement or eat foods with B12 added (fortified foods).
Over 65? B12 or folate deficiency affects about 1 in 20 people aged 65 to 74 and 1 in 10 aged 75 or over.
Your next move: note which of these could apply to you before you see your GP.
Which line shows why it’s low?
That line is your MCV. It’s the average size of your red cells. One NHS lab puts the adult range at 80 to 100 fL (femtolitres, a tiny unit of size).
Back to the vans. The count says how many there are. The MCV says how big they are, and size hints at what went wrong.
| Your MCV | Can be linked to |
|---|---|
| Low (small cells) | Lack of iron, long-term inflammation, or thalassaemia, an inherited blood condition. |
| High (large cells) | Lack of B12 or folate, liver disease, an underactive thyroid, pregnancy or alcohol excess. |
Check your haemoglobin too. One NHS lab’s range is 130 to 170 g/L for men and 120 to 150 g/L for women.
MCV is a clue, not an answer. Your GP will weigh it with your symptoms, history and other tests. More on these lines in our full blood count guide and haemoglobin levels by age.
Your next move: find your MCV and haemoglobin on your sheet and take both to your GP.
What happens after a low RBC blood test?
What usually happens after a low red cell count
- 1
Questions
Your GP asks about your lifestyle and medical history.
- 2
More blood tests
May include iron, B12 or folate tests, or a count of young red cells.
- 3
Poo test
If the cause isn’t clear, a FIT test may check your poo for blood.
- 4
Treat the cause
Depends on the cause, such as iron tablets for about 6 months, or B12 or folic acid.
Sources: NHS: iron deficiency anaemia; NHS: B12 or folate deficiency anaemia; MedlinePlus
NICE says to offer the FIT poo test to adults with iron deficiency anaemia. It looks for hidden blood, to help decide if you need bowel checks.
It also applies if you’re 60 or over with anaemia, even without low iron.
B12 is usually given by injection at first. Folic acid tablets usually need to be taken for 4 months. Your GP may repeat your blood tests over the next few months.
Keep iron tablets out of reach of children. The NHS warns that an overdose can be fatal in a young child.
Before your GP appointment
- Write down your symptoms, such as tiredness, breathlessness or noticeable heartbeats.
- Note if your periods are heavy, or if you could be pregnant.
- List every medicine you take, including ibuprofen, aspirin and stomach acid tablets.
- Say if you’re vegan and don’t take B12 or eat foods with B12 added (fortified foods).
- Ask for your full results, including haemoglobin and MCV.
Sources: NHS: iron deficiency anaemia; NHS: B12 or folate deficiency anaemia
Never stop or change a prescribed medicine without your prescriber. Already on iron? See iron tablets not working.
Low red and white blood cell count
Red cells are made in your bone marrow, the spongy tissue inside your large bones. White cells come from there too.
So some causes show up on both lists. Bone marrow damage from infection or treatment like chemotherapy can lower white cells. Cancers that affect the bone marrow, such as leukaemia, are on both lists as well.
Alcohol excess, liver disease and some medicines can lower white cells too.
Your next move: ask your GP what the two results mean together. See our white cell count guide for how that line works.
When to speak to a GP
Results usually come within a few weeks. Book an appointment if:
- You’re tired, breathless, have noticeable heartbeats, paler skin or headaches. These can be signs of iron deficiency anaemia.
- You have extreme tiredness, pins and needles, a sore red tongue, mouth ulcers, weak muscles or vision problems. Or low mood, anxiety, confusion, or trouble with memory, understanding or judgement. B12 or folate deficiency should be treated as soon as possible, as some problems can be permanent.
- You have any of these: paleness, tiredness that won’t go, swollen glands in more than one place, or a swollen liver or spleen. Or fever, repeated infections, bruising, bleeding or tiny red spots on your skin you can’t explain. NICE says to consider a very urgent blood count.
- You’re 60 or over with anaemia, or have iron deficiency anaemia, and haven’t been offered a FIT poo test.
Call 999 or go to A&E if you’re vomiting bright red blood or your vomit looks like ground coffee. The same goes if your poo has blood in it, or is black, sticky and very smelly. Or if you have severe tummy pain, it hurts to touch your tummy, or you get sudden chest pain.
See also the anaemia blood test and iron deficiency blood tests.