Fasting on Yom Kippur – Part 5: Mikvah on Erev Yom Kippur

BS"D

Think about what the pump sees. It sees the insulin it thinks it has delivered, and it sees your sensor readings. That is all the information it has. It does not know whether the insulin actually reached you, and it does not know whether the reading is right.

This post is mostly about the sensor, because the sensor is the one you cannot take off and put back. The infusion set is a second layer on the same idea.

And the rule is the same for both. Nothing on your body should be starting its first day when the fast begins, and nothing should be due to run out in the middle of it.

In this post:

• The sensor's first day is its worst day
• And it must not run out during the fast
• Now to the mikvah, which is where this goes wrong
• What I would suggest – move the clean tevilah earlier
• The infusion set – the second layer
• What happened to me on Rosh Hashanah
• Which is why it goes in Sunday morning, not Sunday afternoon
• The plan for this year in short

The sensor's first day is its worst day

A sensor is at its least accurate in its first day. Anyone who has worn one knows the feeling – the first hours read a little off, and by the next day it has settled.

A sensor started on erev Yom Kippur afternoon is sitting in that first day exactly when the fast begins. Kol Nidrei, the night, the early hours of the next morning – the whole opening stretch of the fast, run on the least reliable readings that sensor will ever give.

So the sensor should have a full day behind it, at the very least, when the fast starts.

And it must not run out during the fast

The other end of the sensor's life matters just as much, and it is the one people forget. Check the sensor end date before you decide anything else.

A sensor that ends on Yom Kippur afternoon leaves you with nothing to look at for the hours when you most need to look. And replacing it on Yom Kippur only moves the problem: now you are in the first day, on the fast day itself.

Best when the sensor is still running until the morning after the fast. That gives you a window, and it is a narrow one. Old enough to be past day one. New enough to last past the end.

Now to the mikvah, which is where this goes wrong

Everything above is manageable on an ordinary week. What makes erev Yom Kippur different is the mikvah.

Our Rav has already ruled on the basic question, in the halacha post we published from the Shabbaton. For a man, a sensor is not a chatzitzah at all.

But there is a reason people are uneasy on this day in particular, and it is a real one. The Mateh Efraim writes (siman 606, se'if 8) that although during the rest of the year one need not be medakdek about a chatzitzah on a mi'ut haguf – a small part of the body – on erev Yom Kippur one should be careful and medakdek even on a mi'ut haguf.

A sensor and an infusion set are precisely that case. A small part of the body. Which is why this is the one tevilah in the year where a person who is not otherwise particular feels that here he should be.

And that is the collision. A clean tevilah means taking both off – and whatever you put on afterward is only hours old when Kol Nidrei starts. A sensor in its first hours, carried into a twenty-five hour fast. That is the exact situation this post exists to prevent.

If it comes to it, we go to the mikvah with them on. There is no choice. Getting accurate readings from your sensor is more important now. Remember that the erev Yom Kippur tevilah is a minhag, not a chiyuv.

What I would suggest – move the clean tevilah earlier

This next part is my own suggestion.

Go to the mikvah with nothing on your body once in the last days before Yom Kippur – as close to Yom Kippur as you can manage, so that it is a tevilah that belongs to Yom Kippur. No sensor, no set. Have in mind that this tevilah is for Yom Kippur. Then on erev Yom Kippur itself you go in with them on, the way you have to, and the dikduk has been kept.

For this year's calendar, where Yom Kippur begins Sunday night, Friday is close enough to Yom Kippur to count and far enough from it to be safe. Go to the mikvah on Friday, any time during the day, with nothing on. Put the new sensor and a set on right afterward.

The sensor is then two and a half days old when the fast starts, well past its first day, and still running long after the fast ends. That is the whole point of moving the tevilah, and it is why Motzei Shabbos is too late – a sensor put on Saturday night is still in its first day at Kol Nidrei.

The infusion set – the second layer

You cannot know that an infusion set is working until enough time has passed with insulin going through it. Not an hour, and not on the word of the pump, which has no way of telling you that the insulin never arrived.

The set you put on after the Friday mikvah will not do for the fast – it will already be in its fourth day on Monday evening. So put in a fresh set on Sunday morning, erev Yom Kippur. That leaves the whole day of erev Yom Kippur eating to prove it's working before Kol Nidrei.

What happened to me on Rosh Hashanah

I changed my infusion set on erev Rosh Hashanah, in the morning. It felt a little sore going in, but it seemed to be working fine.

It was a busy day. I was packing up to travel to Brooklyn, and I did not eat much. My blood sugar stayed in range.

The first night of Yom Tov, after the seudah, my numbers were not acceptable. Not catastrophically high. But not acceptable. They stayed higher than usual for the whole night – higher than a regular night, and higher even than a typical Friday night.

I woke up at alos, 5:20 in the morning, and I was 170. That is not acceptable for me.

The site was still sore. I figured something must be wrong. And I was about to daven Mussaf before the amud, as the baal tefillah. I could not take a chance, so I put in a new set.

When I pulled the old one off, two things were noticeable. The cannula was slanted, which is not the end of the world. But the edge of the cannula was crimped. Kinked.

I cannot really explain how my numbers were fine the whole day after the insertion. It seems a little insulin was getting through – enough for basal – but the large amount needed for a meal could not make it through.

Whether that explanation holds or it does not hold, the lesson is the same. You need ample time on a new infusion set to decide whether it is working properly.

Which is why it goes in Sunday morning, not Sunday afternoon

A set put in early on erev Yom Kippur has the day's meals behind it before the fast begins. A set put in late has one meal behind it, and that meal is the seudah hamafsekes – on the clock, with Kol Nidrei coming. Finding out then that the set is not delivering is the worst possible moment to be putting in another one.

And if the site is sore going in, that alone is reason enough not to take it into the fast.

The plan for this year in short

Friday, any time during the day. Mikvah with nothing on. New sensor and a set right afterward. Check the sensor's end date first, so it is still running on Tuesday morning.

Sunday morning, erev Yom Kippur. A fresh infusion set, early in the day. If the site is sore, change it – do not take a sore site into a fast.

Sunday afternoon. Mikvah with the sensor and set on. Nothing new goes on after that.

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We have been given wonderful tools, and on a fast day they carry more weight than on any other day of the year, because there is nothing else to check them against. All this post is asking is that you walk into the fast with tools that have already proved themselves.

Wishing you a gmar chasima tova and an easy fast.

– Rabbi Hirsch Meisels