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Macrocytosis and Sprycel


My consultant has told me that my red blood cells are larger than normal (macrocytosis). I've read MartinZA's post where he mentions developing macrocytosis while on Sprycel with interest. My B12/Folate levels are good.

Anyone else experiencing this side effect with Sprycel?

Hi Rosiem

Every since starting my TKIs I've had macrocytosis - it basically means that the red cells are wider in diameter than they are supposed to be.  This makes it harder for them to move in the body and means that it is harder for them to transport oxygen effectively, at least according to how I understood my doctor's explanation.  She told me that macrocytosis isn't really something to worry about, but that it can cause fatigue / being short of breath.  I have personally wondered whether it is somehow linked to the development of pleural effusions on Sprycel, but keep forgetting to ask.

Since I changed to imatinib I have still had the macrocytosis.  Apparently it is measured by three indicators on the blood test:  MCV, MCH and RDW.  I'm not really sure what each of these means, but my tests always show these slightly elevated (just a few points above normal).  But I haven't given it much thought since my doctor isn't concerned about it.

I'm not sure that this helps very much, but I thought I should give you a bit more information!

Best wishes



Macrocytosis can be a common thing. I also have an elevated MCV. Below you see link to two research papers where it is concluded that elevated MCV (macrocytosis) can actually be a surrogate marker for a durable cytogenetic response from the TKI treatment. Of course, it is not for certain, but at least there is some scientific research on this matter. Whether it is completely true or not, hard to say.



Macrocytosis is common with TKI treatment especially dasatinib. It often accompanies lower red blood cell count than normal (mild anemia) due to TKI induces myelosuppression. As long as hemoglobin amount is normal or near normal, the lower red blood cell count adjusts with each cell enlarging to hold more hemoglobin. It is generally benign. The red cells are not so large as to not flow easily around the body.

I have/had macrocytosis throughout my TKI treatment. I have been off dasatinib for over six months now that my CML is "undetected" and my red cells are still enlarged somewhat, but it does seem to be decreasing. I'm surprised how slow the reverse process is taking. May be due to the fact red cells last months in the body.

Hi Timo

Thanks so much for these informative articles - very interesting!  So this macrocytosis may be a good sign? Either way, I don't think it is too much to worry about.

Best wishes


Thanks Martin ZA for your feedback. I now have something to bring to my haematologist. Perhaps it hadn't occurred to them that the macrocytosis was a side effect of a TKI. My first search on google showed a research paper on TKI-induced macrocytosis.

I was first diagnosed with CML  in Nov 2016 but the larger than normal red blood cells were first mentioned 21st September 2021. I still get breathless walking fast or up steep hills but ok otherwise. The dosage of Sprycel was increased to from 70mg to 100mg on 21/09/21. My last PCR reading was 0.41 on 19/10/21 which is the lowest I've ever had. 

Thanks again,



Thanks Timo,

These references are very helpful and I can pass them on to my haematologist. I must admit I was worried that the larger than normal red blood cells were a sign of a more serious side effect. I'd grown used to the fatigue, swollen eyelids, mouth ulcers, digestive upset, etc but this seemed to come from nowhere five years after first diagnosis. Your feed back is reassuring.


Hi Scuba,

That's relieved a lot of my anxiety, just knowing that other CML sufferers have the same problem of macrocytosis. I just checked my haemoglobin levels and it's the one thing I've never had to worry about (fingers crossed). Great feed back and support so far from the CML community. I'm seeing my haematolgist at the end of November and can present all this information. 



My GP and diabetic nurse do worry about my anaemia. The haematologists are generally not perturbed.

My haemoglobin is always low, as low as 111 in the normal range 130-162. Normally, the haematologist describes my anaemia as normocytic and normochromic, judged by the mean cell volume (MCV). When on one reading the MCV was high, my anaemia was macrocytic. My B12 and folate are always normal. Only on the most recent reading has my iron been out of range.

The anaemia appears to be within the general expectation of the haematologist. I suspect that it is reasonable to assume that this is caused by the TKI.

Thanks Nimbus for that information,

I will check with my Haematologist that my iron levels are good. Usually they only flag something if its outside the normal range.


A blogger in the USA refers to himself as "Trey" hence "Trey's Blog".

His entry there on anaemia includes the following:

CML drugs do a good job suppressing leukemic cells, but for most of us our blood cell counts can go too low, especially after a month or so on the drug. This may continue for years before leveling out. That causes many of us to live on the low end of normal or below normal for WBCs, RBCs, hemaglobin (HGB), hematocrit (HCT) and sometimes platelets (PLT). The result is a type of drug induced anemia and fatigue can result ... Many of us with CML have for the longer term what is called Anemia of Chronic Disease".

It does appear that CML patient on TKIs can be anaemic without having out of range iron, B12 or folate readings. This seems to be a likely explanation of CML fatigue.




Thanks Nimbus 2,

That describes my response to Dasatinib to a tee. Will have a look at Trey's Blog.