Sugar Surfing with my Insulin Pump’s Manual Mode

August 15, 2022

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I use the Medtronic Minimed 670G Insulin Pump, which has two different systems. It has both an “Auto mode” and a “Manual mode.” I started using auto mode after using the pump for 1 week. My trainer taught me how to use auto mode and I was instructed to stay in auto mode most of the time.

Auto mode is amazing. It does a very good job of preventing me from going low. However, as terrific as auto mode is, I’ve realized that I can actually achieve better control by sometimes using manual mode. I now think of auto mode as like training wheels. Auto mode makes using an insulin pump for the first time less scary, but for increased performance, you remove the training wheels when you’re ready.

This analogy isn’t perfect, because I am still choosing to use auto mode while sleeping, and I also do use automode on some days. It is helpful especially when I’m having a day when I need less insulin. But, automode doesn’t do a great job during time periods where I need more insulin than usual. For example, in the morning I usually need more insulin than normal, and this is even more true on work days. On work days, I am sedentary and have more stress and both of those things combined means that I need more insulin. Every morning I was going high when in auto mode, but since I’ve started to use manual mode, I am able to stay in range by increasing my basal rate during these stress filled mornings.

Not all stress is bad. I actually enjoy my work. However, it still holds true that I need more insulin on work day mornings and I’ve found recent success by switching to manual mode and setting a higher basal rate to keep my blood glucose in range.

The Results aren’t Always Perfect

One of the things that motivated me to try manual mode is that I read the book Sugar Surfing: How to Manage Type 1 Diabetes in a Modern World and I felt empowered by that book. I realized that I couldn’t apply all of the techniques described in that book while being in auto mode!

A big take away from that book was that by knowing myself and using predictions about myself, I can use that to optimize insulin delivery. If I always need more insulin on work day mornings, then I can program the insulin pump to deliver more then. If I’m really hungry because I haven’t eaten much all day, then I know I will be eating and snacking a lot soon, so I may as well bolus some insulin because I’m about to eat a lot! Even if I don’t yet know what exactly I’m going to eat, I can guess that it’s going to be at least a certain number of carbs and I can start planning for that. Insulin takes times to work and the book talks about several techniques on how to improve that timing. Another example is stalling for time if you need to wait for your blood glucose to drop a bit before eating.

The other point that the book makes is that people without diabetes actually have a blood glucose under 100mg/dl for a good period of time. I realized that my blood glucose was mostly between 100mg/dl-200mg/dl and that I’m averaging about 150mg/dl instead of 100mg/dl. This is considered good control however this is not the same as having a normal number. It’s like because of the danger of going low, the medical community generally accepts that diabetics will have a higher average blood glucose than people without diabetes. This can be seen in the guidelines for understanding A1C test results. It is expected that a person with diabetes who has it well controlled will still have an A1C higher than someone without diabetes.

The Medtronic 670G Insulin Pump sets a target goal of 120mg/dl when in auto mode. However, what I found is that most of the time that meant I was above 120mg/dl. Like literally I’d never be lower than 120mg/dl during the day unless I did a larger than needed bolus. Psychologically the issue is that there’s rarely an opportunity to be like “hey, this is a good time to eat a cookie!” whereas in manual mode you can program it so that you will continue to trend downward slowly and then when it looks like it’s going to go a bit low, you’re like, time for a cookie!! It’s not fun to bolus and then wait 20 minutes to eat the cookie. It’s more fun to set yourself up for this slow downward trend and then to correct it with a cookie. Of course, that cookie may be too much of a correction and without additional insulin or exercise, you may see a sudden rise from eating the cookie. It’s not necessarily as simple as I’m making it sound, but if you enjoy being at 80mg/dl and having something sweet to eat, then I’m just saying that auto mode doesn’t really give you that opportunity.