Everything you wanted to know about the effect that time of day and fasting has on serum iron...in one paragraph.

The researchers analyzed upwards of 250,000 iron tests and concluded the following. Does this have any implications for RLS?

researchgate.net/publicatio....

[Bluebboat]

Trying to get article. You have to request it and then wait.

[Hidden in reply to Bluebboat]

Here is summary: Objectives: Serum iron is an important clinical test to help identify cases of iron deficiency or overload. Fluctuations caused by diurnal variation and diet are thought to influence test results, which may affect clinical patient management. We examined the impact of these preanalytical factors on iron concentrations in a large community-based cohort. Design and methods: Serum iron concentration, blood collection time, fasting duration, patient age and sex were obtained for community-based clinical testing from the Laboratory Information Service at Calgary Laboratory Services for the period of January 2011 to December 2015. Results: A total of 276,307 individual test results were obtained. Iron levels were relatively high over a long period from 8:00 to 15:00. Mean concentrations were highest at blood collection times of 11:00 for adult men and 12:00 for adult women and children, however iron levels peaked as late as 15:00 in teenagers. With regard to fasting, iron levels required approximately 5h post-prandial time to return to a baseline, except for children and teenage females where no significant variation was seen until after 11h fasting. After 10h fasting, iron concentrations in all patient groups gradually increased to higher levels compared to earlier fasting times. Conclusions: Serum iron concentrations remain reasonably stable during most daytime hours for testing purposes. In adults, blood collection after 5 to 9h fasting provides a representative estimate of a patient's iron levels. For patients who have fasted overnight, i.e. ≥12h fasting, clinicians should be aware that iron concentrations may be elevated beyond otherwise usual levels.

[Guitarpickin in reply to Hidden]

That is so weird! I assumed the longer the fast the more accurate the reading would be! I know nothing, so to you (or someone who understands), does it make sense the iron level would actually increase after 12 hours of fasting?

[Hidden in reply to Guitarpickin]

Kind of. I can practically hear our bodies barking out orders, "food is in short supply, tell hepcidin to back off, release the ground supplies (including iron)."

[Bluebboat in reply to Hidden]

The trouble with this is is that it modifies the theory that increasing serum iron helps suppress rls as my legs are often quite bad early morning.

[Bluebboat in reply to Hidden]

Still I think you are right on the case…whole theory just needs refining and strengthening with more research. Please keep going.

[Hidden in reply to Bluebboat]

I lack the formal education and sheer brain capacity to refine theory. I’m hoping someone else will pick up baton and run with it. However, I’m beginning to think it’s worth it to have both ferritin and serum iron in a high healthy range.

[Gmc54]

Can't access the article. I'm ticking not a researcher then I can go no further sadly.

[Hidden in reply to Gmc54]

Here is summary: Objectives: Serum iron is an important clinical test to help identify cases of iron deficiency or overload. Fluctuations caused by diurnal variation and diet are thought to influence test results, which may affect clinical patient management. We examined the impact of these preanalytical factors on iron concentrations in a large community-based cohort. Design and methods: Serum iron concentration, blood collection time, fasting duration, patient age and sex were obtained for community-based clinical testing from the Laboratory Information Service at Calgary Laboratory Services for the period of January 2011 to December 2015. Results: A total of 276,307 individual test results were obtained. Iron levels were relatively high over a long period from 8:00 to 15:00. Mean concentrations were highest at blood collection times of 11:00 for adult men and 12:00 for adult women and children, however iron levels peaked as late as 15:00 in teenagers. With regard to fasting, iron levels required approximately 5h post-prandial time to return to a baseline, except for children and teenage females where no significant variation was seen until after 11h fasting. After 10h fasting, iron concentrations in all patient groups gradually increased to higher levels compared to earlier fasting times. Conclusions: Serum iron concentrations remain reasonably stable during most daytime hours for testing purposes. In adults, blood collection after 5 to 9h fasting provides a representative estimate of a patient's iron levels. For patients who have fasted overnight, i.e. ≥12h fasting, clinicians should be aware that iron concentrations may be elevated beyond otherwise usual levels.

[Gmc54 in reply to Hidden]

Thank you for this.

[PoorRichard]

Given this info, what does it imply for a realistically optimal time for blood draw?

[Hidden in reply to PoorRichard]

Good question. I have to think about that.

[WideBody]

I have the full study. If anyone wants it, feel free to PM me.

BTW, I don't full understand it either.

[Munroist]

Main implication seems to be that if you fast for a long time overnight before your test e.g. > 12 hours , your iron levels may read a bit higher. For most people though the advice is leave 5 - 9 hours after eating and test between 9:00 and 15:00 to get the best result.

[s_gc]

Interesting study. That means that my readings for iron over a six-month period are in reality even lower than they show... Definitely need an infusion as months of iron supplements intake didn't do much at all to raise the levels (although it did stop a period of very bad symptoms that at the time stopped me from sleeping for more than 3-4 hours)!!

[Hidden in reply to s_gc]

Good luck with that infusion. Not for me. I could get my ferritin up to 3000 and I guarantee I would still need to take that nightly supplement of ferrous bisglycinate. Have you tried fasting after 7pm and until breakfast - night, after night, after...?

That may get you to 100% relief from symptoms of RLS.

[s_gc]

Thanks Hidden , 90% of the time (and especially in lockdown) I eat before 8pm and do not eat anything until 13h00 the day after meaning I am 'fasting' for over 12hours (it's just I don't feel like eating and then since I don't cycle anymore to work I don't need the energy either).

As for the infusion it may not work but I just want to give it a go. My ferritin level remains truly low after 6 months of supplements at high dose of iron (2 or 3x67mg of iron), it only went up from 24 to 36. Apparently it's in the family, my body is just not able to absorb much iron at all 😔...

[Hidden in reply to s_gc]

I would not be discouraged with the supplements. I would switch to the ferrous bisglycinate when you can afford to do so and ONLY take it an hour before bed on an empty stomach. Even with whatever form of iron you are taking now I would take the full dose before bed only. Keep us posted about both - supplements and infusion.