Doing a fasting test today

[swttbsy5]

My Endo has suggested that I do a fasting test to rule out insulinoma, as I have sometimes hypo'd while fasting. She has given me forms to do the blood test if/when my glucoe level drops to 2.7 or below. I have someone who is ready to drive me to the pathology clinic anytime, if need be. The tests she has ordered are for: Glucose, Insulin, c-peptide, cortisol, proinsulin, beta-hydroxybutyrate, sulphonylurea - in the event of low glucose. There is another test form with some extra things on there too: insulin antibodies, FBE, UEC, LFT, TFT, prolactin, ACTH, IGF-1, chromogranin A. I have been fasting since 5 pm yesterday and it's now 9 am and my glucose level is sitting stable at 4.3. The last time I had a hypo while fasting, I got a reading of 2.7 after skipping breakfast one day and then only eating a steak for lunch, then waited about 4 hours while the level slowly dropped.

These are my previous results from 2018:

Pathology Jan 2018 EGFR >90 LFT normal TSH 3.61 mIU/L (0.40-3.50) FT4- 12.1 pmol/L (9-19)
OGTT 75g fasting glucose 4.9, 2-hour glucose 2.1 mmol/L

Medical Imaging Feb 2018
CT abdomen and pelvis No focal pancreatic lesion detected. No acute intracranial, intra-abdominal abnormality detected

March 2018
Pancreatic polypeptide 26.2 pmol/L (<55)
Cortisol 350 nmol/L
ACTH 3.9 pmol/L FSH 1.6 mIU/L
LH 3.1 mIU/L
C-peptide 0.69
Insulin 6 Plasma metanephrines normal: normetanephrine 320 pmol/L (<640), metanephrine 190 pmol/L (<447), 3MT <50 Adrenaline 0.1 nmol/L (<1)
Noradrenaline 1.8 nmol/L (<3.5)
Chromogranin A 40 Sulphonylurea screen negative

 

[MarkMunday]

Presumably the logic is that low fasting blood glucose and high insulin levels may mean insulinoma. That your fasting blood glucose is normal suggests this is not the case. Your previous experience with blood glucose dropping suggests the opposite. It may help to use a Libre CGM for a while so you can see exactly what happens to blood glucose overnight. Having something to eat before bed and even exercise or stress the previous day can affect it. Anything that could distort results should really be avoided before and during testing.

 

[Brunneria]

are you still eating very low carb @swttbsy5 to control your reactive hypoglycaemia?
IF so, then that could well explain the hypo last time, and the (so far) lack of hypo this time.

I'm suggesting that if your body is fat adapted now, then it can maintain your blood glucose nice and steadily in the absence of food, because it has ketones as a fuel source too, possibly even the main fuel source. Whereas with your previous test, if your body was used to running on carbs and glucose all the time and those carbs were cut off, your blood glucose dropped sharply, and your body wasn't practised at reaching for alternative fuel.

Obviously, I am speculating.
However, I am speculating because I know how my own reactive hypo prone body functions when on a carby diet compared with a keto diet, and what I have just described is what would happen to me. It is also something that ketoers report regularly, when fasting. The more fat adapted and the deeper their ketosis, then the easier fasting becomes for them. The longer they can fast, and the better they feel during fasting. In fact, they often advise people to only introduce fasting after they have adapted to keto.

Regarding the insulinoma, I am sorry but I don't know how the presence of an insulinoma would impact a ketogenic fasting test. I guess it would depend entirely on the size of the insulinoma and the output of insulin.

 

[swttbsy5]

I fasted for 27 hours. I was stable at around 4.3 for 24 hours and then I started to go low - slowly. I did the blood tests (checking for insulinoma) at a level of 3.6 which is unfortunate because it's supposed to be done when bgl is lower than 2.8 but the pathology place was closing for the night so I had to do it then. Later the level dropped lower down to 3.3 when the hypo symptoms started. I had some cashews and macadamia nuts and full fat cheese with me so I ate that and then about 15 minutes later I went down to 2.9. I then had a half glass of milk and a strawberry and went quickly back up to 5.3 and now stable (I hope) in the high 4's. Seriously not sure what is going on here but I'm pretty sure this is not normal for normal people or it seems for RH either. I'm feeling very concerned about these results and I guess the next thing to do is a 72 hour in hospital fasting test. Also, at one point the ketone level was at 3.8 which I believe is very high? The endo said if my ketone level gets above 4 that I should increase from 50g to 100g carbs per day.

And yes @Brunneria I have been eating very low carb for quite some time now and I haven't stoppped once. I have a carb tracker app and I'm usually under 40 grams per day and I have been very strict with it with good results in terms of bgl stability and now crashes etc.