I just got the results of the blood test back. There are three numbers that seem to be in conflict with each other and with my expectations:
Glucose 60mg/dl expected range 60-125
Fructosamine 1.89mmol/l expected range 0.00-2.09
Hemoglobin A1C 5.6% expected range 3.0-6.0%
So, I am at the bottom end of the glucose range, but near the top end of Fructosamine and A1C. From what I've read, those two are markers indicating long term blood glucose levels. I've been Paleo for 18months, the last 8 months of which I have been either low carb or very low carb.
I'm not alarmed or anything; I just want to understand what this might indicate about how my body processes macronutrients. I have always found it difficult to get reliably into ketosis. I have to drop to very low carb levels to do so. My wife, on the other hand, can momentarily drop a few carbs, and she pops straight into ketosis.
Could my difficulty getting into ketosis be related to the numbers above? Do those numbers tell me anything that could steer me to an optimal carb level?
Glucose is a one-time measurements of what your blood sugar levels are at the specific time when your blood is drawn (whether you were fasting or ate in the hours before, whether you exercises, your hormones fluctuations for females, if you are fighting an infection all influence your results).
A1C reflects approximately the last 3 months at ALL TIMES. Again, the same factors that influence your glucose levels can influence your A1C and eating a clean Paleo diet can also make your A1C go slightly higher if it stays longer than 3 months in your blood.
Fructosamine is similar to A1C but reflects your "average" blood sugar levels in the last 2-3 weeks. Again, I presume that like A1C, a Paleo diet may slightly elevate these results in some people.
I think that taken alone, these numbers do not indicate an awful lot. What would be nice is to compare them to previous results or have these measured in 2-3 months again to see if thing are getting better.
For example, some studies suggest that if your A1C is high, it is most likely that your blood glucose levels are high throughout the day and when fasting. The closer your blood glucose levels are to the ideal A1C range, the more your postprandial glucose levels (after meals) contribute to the number.
I don't know much about the fructosamine measure; but, the A1C is totally explainable: Chris Kresser talked about this a long time ago, but A1C is invalid when you're really healthy. The way I interpret his explanation (and you should go see what he says and the the info from the source itself) is that A1C is the fraction of your RBCs that are "ruined" from high sugar and are still lingering around in your circulation. The numbers that are deemed "good" or "bad" are from looking at the population average; however, once you start getting healthier, your red blood cells live longer and it throws off the measurement.
Think of it this way: there's a certain lifetime for a RBC (I think it's around 90 days), and during that time there's a certain percentage that it'll get ruined by sugar (from AGE formation), that number is the A1C. So an A1C of 5 means that in 90 days there's a 5% probability of a RBC getting ruined. (Roughly).
But if your RBCs live longer because you're eating better, they have a longer time to encounter some sugar. So let's say (to make the numbers easy) that a person eating healthy has RBCs that live to 180 days. A measured A1C of 5 means that in 180 days there's a 5% probability of a RBC getting ruined. However, that needs to be normalized to the standard measurement and gives an effective A1C of 2.5 (because they lived twice as long, they have more time to encounter problems, but the test doesn't know that - it only looks at a snapshot in time).
Basically, if your RBCs live longer than the calibration of the measurement assumes the the number you get back is meaningless. It's best to go see what Chris says about this, but that's my simple physical picture of the issue: you need to know what's being measured and what it means.
For a healthy eater the A1C is not useful, and will often be reported higher than it really is.
Your A1c of 5.6 would indicate an average glucose level of 122, which seems unlikely given that you've checked after meals. Your fructosamine would indicate a much lower average glucose level and an a1c of 4 something; I've nto seen a chart that goes below 5.
The after meal checks are the only way I know of to estimate the carb level (and time of day that carbs work for you) as well an more accurate idea of your A1c. I am pretty agnostic on the idea of ketosis. I am not sure it is a good idea to be there all the time (see Hyperlipid) so I just try to avoid being hungry.
You might be interested in this paper - free full text - "Is there a glycemic threshold for mortality risk?" http://care.diabetesjournals.org/content/22/5/696.long