Hydration and Haemoglobin / Haemotocrit Levels

[Lettie_WP]

Does anyone know how much hydration can affect haemoglobin and haemoticrit levels?

Ever since the prospect of PV was raised I have been sure to be very well hydrated before my blood tests. (I have them mid afternoon generally and ensure i have drunk 2l of water before hand). I realise that in the past I wasn't drinking enough water, but am i now 'fudging' the result? My pre bothering to drink much water levels were around 162 - 166. Now, they are around 149 - 153. Could it just be the water, and that actually there has been no (miraculous) improvement? (I'm on no meds or anything. Jak2 neg, but EPO still low at 3.6).

[katiewalsh]

I don’t know about those numbers but since my platelet numbers can vary based on how hydrated I am I wouldn’t surprise me if they all can. And blood lab results from lab to lab. What’s important is to talk to your doc about how much water s/he wants you to drink daily & be religious. Many of us try & drink 2-3 liters daily. Katie

[Beerye1]

I don’t know if I’m much help at all but I’ll drop this comment anyway: I was on this forum last year because I had abnormal bloods (175hb and 51hct) which was odd for a 27 year old non smoking female, doctor suspect PV. I got all my referrals and had more bloods done by my haematologist and those ones came back as 135hb and 41hct. Ultimately in the end my haematologist thinks hydration was a big factor in my abnormal results, he said something along the lines of ‘some people are just really sensitive to dehydration more than others’.

My uncle gets it too, if he’s even a little bit dehydrated his bloods are a bit out of whack, he’s 65 and has absolutely zero evidence of any MPN or literally any other disorders at all, healthy as a horse 🤔

[Lettie_WP in reply to Beerye1]

Thanks Beerye1.

[hunter5582]

The short answer to your question is yes. Hydration does affect HCT since it increases plasma volume. HCT is a calculation that includes plasma volume.

"Both the hemoglobin and the hematocrit are based on whole blood and are therefore dependent on plasma volume. If a patient is severely dehydrated, the hemoglobin and hematocrit will appear higher than if the patient were normovolemic; if the patient is fluid overloaded, they will be lower than their actual level."

ncbi.nlm.nih.gov/books/NBK2....

Hydration is a good thing. It is why good hydration is important to stay well hydrated when you have PV. The most accurate way to know your "true" HCT is to be consistent with hydration - do not drink more or less prior to a CBC.

[Lettie_WP]

Thank you hunter5582. I have been sure to drink the same amount before my last 4 blood tests (also taken at roughly the same time of day). The results have been more of less stable (very high / borderline normal or very slightly over). So hopefully I now have a baseline to work from.