Interpreting overnight basal test



Without knowing how effective the Medtronic suspend feature is nor knowing how effective the Medtronic sensor is and not wanting to run down the rabbit hole and spin your thread out of control…
But in general - yeah - that certainly would make sense to be more comfortable with a more aggressive approach if you feel that you have technology that is watching over you.


@LarissaW, I see that @Michel is typing as I am typing…which makes me a little nervous to contribute amongst the well-respected big leaguers here (@Thomas, included)…but, take my analysis with a grain of salt, fwiw.

I find basal testing to be helpful, and hard to exactly predict. So I just try, try again until it seems acceptable. Which is what you are doing.

Per your fingersticks, you lost 66 points over 9 hours. Per Dexcom, you lost 46 points over 9 hours. From 8PM - 6AM, you are currently using 9.25 units of basal. Your proposed changes would take you down to 9.175 units of basal. A modest change.

Looking at the general shape of the graph, aside from the last drop it looks pretty steady with a slight downward slant. When I see stuff like this on my graph, that typically means the relative rates themselves are accurate in relation to each other…but it is just slightly too high overall and is gaining steam as the night goes on. In this scenario with my current basal rates, I’d do a 5% reduction across the board. That may or may not be the right call…but you are in Week 2 hormones which we want to get as flat as possible (if your body acts like mine…which it may not)…so maybe do a slight reduction off each time period.

BUT, that might not work and maybe just one timeframe has to be tinkered with. Overall, your night looks safe to me. But clearly an adjustment of SOME kind would make it flatter and safer, especially if you have to scale it up for hormones in Weeks 3 or 4. Which you may not be as sensitive to as I am.


Let’s save this for another day :sweat_smile::sweat_smile::sweat_smile:


O please! Any opinions are helpful for me here!!!

Ah, I like this way of looking at total basal over time. Definitely adds perspective on it.

That would agree with last night’s basal test but less so with the basal test I’d done previously… which is making me think maybe one more “baseline” test would be helpful… but there’s only so many of these nights in this relatively stable Week 2 before I’ll have to wait 3 weeks to retest…


Possibly you are not dealing with severe hormone peaks like us? We find that we must deal with the true DIA as soon as we stack (very often on peaks) or use very large boluses. If we don’t, we run into bad persistent lows. So we look at both numbers for different purposes: the true DIA and the typical effect duration of one injection.

I believe there is mention of this phenomenon (true DIA length vs pump DIA) in one of the bibles of D (sugar Surfing, Think like a Pancreas, pumping Insulin?) But I don’t have them at hand to quote.

I feel it is important for people to be aware of this effect of the true DIA, because the consequences of not knowing it could be, truly, deadly (ref the story of the poor guy who died w his CGM on—not same issue, but could end the same way).

Often true for us. It takes us a week or so before we are ready to believe in a time-based pattern.

@LarissaW wrote she saw an impact from FIASP in 5-15mns. This is totally not what we are seeing with Novolog (we see about 1 hour delay), but @thomas once wrote he saw almost immediate effect with FIASP. So it could be YDMV. Although anything below 45mns on basal changes still seems amazing to me.

[quote=“Beacher, post:9, topic:6346”]

it’s impossible to know from one night’s line (…) Personally I’d give it a week and then see if there’s a trend [/quote]

Agree with @Beacher.

Agree with @Thomas

Normally I am a big proponent if this logic: one step at a time then evaluate. But, for basal adjustment, I think you would be better off looking at it in a different way.

A single change means that you will either decrease or increase the total amount or insulin in your night. But does your night need more, or less, or the same? For a first order analysis of that, you look at both ends: where you started and where you ended. If the two ends are more or less equal, then any change to your basal profile must more or less respect the total amount you inject now. Therefore, any single interval change would need a opposite change somewhere else.

Of course, this is approximative. Still, I think if you are roughly even for the whole night, and decrease your basal 10-15% for 2 or more hours, you will likely end up higher in the morning, and vice versa. So, Imho, each change you make to a roughly balanced basal needs an opposite change :slight_smile:

I find this thread very interesting in the difference in everyone’s approach!


If it were me, what I would do is try the test again tonight with clean data from 10PM on (meaning eat early again). I don’t know if you can do a percentage reduction on your pump. But I would do a 5 or 10% reduction of basal overnight and see if you get a different shape to your night. You don’t have sizeable individual spikes or dips…at least not anything I would trust as a spike or dip per Dexcom’s slight variations. That lack of significant dip or spike tells me the shape of your basals is probably pretty darn close…but the overall magnitude of insulin is too high right now.

And I could be COMPLETELY wrong. But that is what I would try tonight.

[For background, I’m on Day 19 of my hormone cycle. I just increased from +10% basal to +15% basal as of yesterday afternoon. My flat Week 2 numbers start steady climbs as my hormones increase pre-ovulation through Day 23. Day 23 is my worst hormone resistance typically due to the peak progesterone then. And then it meanders back down slowly. Point being, for MY body as a woman, when the whole graph tilts up or tilts down, it’s time for me to scale the whole thing up a bit or down a bit.]


And I would rather make adjustments to try to flatten out overnight and remove the risk of hypos for the next 3 weeks before testing out the changes

Know of any way I could test this? I’d be happy to do so unless @Thomas has experience on FIASP and basal timing?

I’m thinking since both nights have ended up [slightly] lower than where I started I need slightly less in total to end up the same as where I started (which is my goal), so I’m liking @T1Allison 's idea:

going off of


Sorry for so many quotes. I like them to keep my thoughts together :sweat_smile:

And @Michel agreed! I’m learning a lot by seeing all the approaches and thought processes!


Just want to confirm we’re all talking basal changes, not bolus action. So if @Thomas has a basal change at, say, 1 a.m., he sees that reflected almost immediately after 1 a.m., and @LarissaW would see it reflected in 5 to 15 minutes? Wow, that would sure make my life easier.


I see a bolus action around 5-15 minutes but have no idea for basal changes (still new to 1. FIASP and 2. trying with diabetes). @Thomas have you seen similar action times for bolus and basal?


I will be curious to see if you experience similar resistance/sensitivity swings like some of us other female FUDders.

And even if tonight’s test ends up with confusing results…at least you’ll have a good idea of what to watch for in the coming weeks as you observe everything. I have some days where I need an extra 15% in the daytime but only 10% at nighttime. It’s all just best guesses…and help from the CGM. I’m just shooting for the closest ballpark I can get.


I can speak from general experience what I’ve noticed is that I’m way more sensitive a few days leading up to my period and in the beginning of my period. I didn’t know the hormones had an impact until recently (mostly because I had swings all over the place daily and I’d been too lazy to pay attention) so I’m thinking of continuing basal testing at least over nights to get a better idea of my personal sensitivity/resistance throughout the cycle


my life has turned into one big experiment


Preach, sister. I’ve been saying that for months.

You take about twice the basal I take. I wonder if percentages will pan out for you similarly or not. For me, a 5% change is needed when I see about a 40 point stuck difference from what I expect to see. But that stat is still a work in progress.

Good luck! Happy to try to help anywhere I can!


It is the best way to approach it: that is how we improve BG management. Data is King!


@Michel, i just hope working in a basic science research lab for 5 years has prepared me for this :woman_scientist:


@T1Allison I think I’ll aim to test 3 nights a week for every week of the cycle. Do you think that covers enough ground? I know specific days will have big fluctuations (though am not sure what days they’ll be).

Also I’m happy to make a new topic in the women’s health group for this… I will get into reading those threads once I have a chance to sit down with pencil, paper and coffee I promise


@LarissaW, as a point of reference, a difference of 10% basal over one hour, for us, at night, represents about 20-30 mg/dl. So over a whole night, for us, it would be huge. I am not sure what it will be for you, but I expect that decreasing your whole night by 5% or 10% will make a very big change, maybe much more than you want. YDMV of course. Just be careful!


I think a thread in Women’s Health would be great!

Don’t burn yourself out with testing. If you are generally not doing anything too crazy odd going into bedtime (like unusual exercise or some weird snack before bed), your CGM will help you a lot. When you are starting out, it may be worthwhile to do some legit fasting basal tests overnight during various weeks. Now that I’ve been watching mine for so long on it, I only do actual basal testing during Week 2. But that’s bc I’m already in the ballpark. And I’d say it looks like you might be in the ballpark, too. But keeping an eye on general patterns should keep you safe and learning through the next few weeks.

And I never actually do more than a 5% basal change in one day for safety strategy (personal preference). My hormones tend to ramp up over time and ramp down over time more than straight spiking. But that may be specific to my body. Don’t know. If I have a day that is more resistant than what a 5% change will handle for hormones (which is rare), then I fill in the rest with correction boluses. But you may have a different experience.


I’ll second that. For me, especially with an overnight basal, a change as small as 0.05U over a few hours can have a noticeable effect. Going from 1.0 to 0.8, as @Thomas suggested above, would for me have a HUGE impact.