Many of us have noted, regardless which syringe we use (Relions, BD, Monojects), that the syringes are all very inaccurate and the inaccuracy varies from syringe to syringe of the same brand and lot number.
We were using Monoject syringes at the time and noticed that the amount of insulin in the hub, as well as the markings on the syringes, varied from shot to shot. In order to determine how inaccurate the syringes were and develop dosing with calipers, MJ (Donovan) sent me an adjustable micropipettor. 10 microliters on the micropipettor is equivalent to 1u. This allowed me to determine the exact amount in what was marked as 1u on the Monojects. What I found was that 1u, as marked on the Monoject syringes, varied from 14 - 15.2 microliters or 1.4 - 1.52 units. I tested several Monoject syringes and the majority came out as the 1u actually being 1.46u. I found other syringe brands were not as inaccurate but they all were.
Calipers will help you dose more consistently but calipers are not required to dose. If you are comfortable with dosing without them, it will not affect whether your cat will go into remission. It's just a tool to dose more consistently and, if there is more than one person drawing doses, it allows both people to dose the same. Here is the link to the Harbor Freight 4" digital calipers we use just to provide you with an example. Using a light tracer box under the syringe and a lit magnifying glass to look at it from above will give lots of light to help with dosing.
We made two instructional videos to help you. They are similar but the first one was a little dark but still has some good info that I couldn't remember for the second one. It's most important to recognize that different syringe types (e.g. Monoject, BD, Relion) will have a different millimeter measurement for 1u than I used in the video and where you measure from/to with the calipers will likely be different (especially if you are using BD syringes).
If you are currently using calipers, do not change your measurements based on the info below. Consistency is most important so stay with what you have calculated and been using.
If you are starting out dosing with calipers, you can use the measurements below which will enable you to skip the process of determining the millimeters to 1u provided you are using one of the syringes listed below:
All of these syringes are U100, 0.3cc (the gauge of the needle won’t matter):
Monoject 1.24mm = 1u
ReliOn 1.32 mm = 1u
BD Ultrafine II (Canada) 1.5mm = 1u
BD Ultrafine (US) 1.62mm = 1u
Carepoint 1.2mm = 1u
UltiCare VetRX 1.25mm = 1u
Sure Comfort 1.34mm = 1u
I would suggest that if you are starting out dosing with calipers and your syringe is not listed above, ask around the forums to see if anyone else using calipers has already done the below measurements for the exact syringe type you are using. If they have, you can skip the process in the following paragraph because you will have the measurements you need (i.e. how many mm are in 1u for that syringe type) and you’ll just need to make your chart.
If the above information is not available for your specific syringe type from my chart above or from another member, you’ll need to follow the process below to measure the millimeters to 1u for your syringe.
Please be sure and measure the millimeters in 1u on your syringe type. To do this, find as many near perfect syringes as possible where the zero mark lines up perfectly at the top. Measure all of them to see if you can get a pretty consistent measurement in mm for 1u. It also helps to double check it by measuring between the 1u and 2u marks.
Once you do that, you can calculate the remainder of your doses.
It’s strongly suggested that you use millimeters on the calipers, not inches, to measure your dose so the numbers are easier to deal with (if you use inches, you’ll be working with very small numbers).
I recommend you make a chart that you keep near your syringes. I made my chart in 0.1u doses but you can make yours however you wish.
For example, when I developed this originally, I was using the Terumo U100, 0.3cc, 1/2-unit marking syringes (no longer available) where 1.52mm = 1u and I made this chart:
0.15mm = 0.1u
0.3mm = 0.2u
0.38mm = 0.25u
0.76mm = 0.5u
1.14mm = 0.75u
1.52mm = 1u
etc.
Alternatively, if you don’t want to make a chart, you can use the following formula to calculate the mm measurement for each dose:
Example:
(dose) x 1.5 (conversion number provided for syringe brand) = caliper mm
0.25u x 1.5 = 0.38mm
In addition to the videos, below are written instructions how to use the calipers once you know how many millimeters are in 1u on the syringe type you are using:
TERUMO SYRINGE (above)
MONOJECT SYRINGE (above)
If you have any questions or need any help, please be sure and ask. Many members are using calipers and can help or you can PM me.
We were using Monoject syringes at the time and noticed that the amount of insulin in the hub, as well as the markings on the syringes, varied from shot to shot. In order to determine how inaccurate the syringes were and develop dosing with calipers, MJ (Donovan) sent me an adjustable micropipettor. 10 microliters on the micropipettor is equivalent to 1u. This allowed me to determine the exact amount in what was marked as 1u on the Monojects. What I found was that 1u, as marked on the Monoject syringes, varied from 14 - 15.2 microliters or 1.4 - 1.52 units. I tested several Monoject syringes and the majority came out as the 1u actually being 1.46u. I found other syringe brands were not as inaccurate but they all were.
Calipers will help you dose more consistently but calipers are not required to dose. If you are comfortable with dosing without them, it will not affect whether your cat will go into remission. It's just a tool to dose more consistently and, if there is more than one person drawing doses, it allows both people to dose the same. Here is the link to the Harbor Freight 4" digital calipers we use just to provide you with an example. Using a light tracer box under the syringe and a lit magnifying glass to look at it from above will give lots of light to help with dosing.
We made two instructional videos to help you. They are similar but the first one was a little dark but still has some good info that I couldn't remember for the second one. It's most important to recognize that different syringe types (e.g. Monoject, BD, Relion) will have a different millimeter measurement for 1u than I used in the video and where you measure from/to with the calipers will likely be different (especially if you are using BD syringes).
If you are currently using calipers, do not change your measurements based on the info below. Consistency is most important so stay with what you have calculated and been using.
If you are starting out dosing with calipers, you can use the measurements below which will enable you to skip the process of determining the millimeters to 1u provided you are using one of the syringes listed below:
All of these syringes are U100, 0.3cc (the gauge of the needle won’t matter):
Monoject 1.24mm = 1u
ReliOn 1.32 mm = 1u
BD Ultrafine II (Canada) 1.5mm = 1u
BD Ultrafine (US) 1.62mm = 1u
Carepoint 1.2mm = 1u
UltiCare VetRX 1.25mm = 1u
Sure Comfort 1.34mm = 1u
I would suggest that if you are starting out dosing with calipers and your syringe is not listed above, ask around the forums to see if anyone else using calipers has already done the below measurements for the exact syringe type you are using. If they have, you can skip the process in the following paragraph because you will have the measurements you need (i.e. how many mm are in 1u for that syringe type) and you’ll just need to make your chart.
If the above information is not available for your specific syringe type from my chart above or from another member, you’ll need to follow the process below to measure the millimeters to 1u for your syringe.
Please be sure and measure the millimeters in 1u on your syringe type. To do this, find as many near perfect syringes as possible where the zero mark lines up perfectly at the top. Measure all of them to see if you can get a pretty consistent measurement in mm for 1u. It also helps to double check it by measuring between the 1u and 2u marks.
Once you do that, you can calculate the remainder of your doses.
It’s strongly suggested that you use millimeters on the calipers, not inches, to measure your dose so the numbers are easier to deal with (if you use inches, you’ll be working with very small numbers).
I recommend you make a chart that you keep near your syringes. I made my chart in 0.1u doses but you can make yours however you wish.
For example, when I developed this originally, I was using the Terumo U100, 0.3cc, 1/2-unit marking syringes (no longer available) where 1.52mm = 1u and I made this chart:
0.15mm = 0.1u
0.3mm = 0.2u
0.38mm = 0.25u
0.76mm = 0.5u
1.14mm = 0.75u
1.52mm = 1u
etc.
Alternatively, if you don’t want to make a chart, you can use the following formula to calculate the mm measurement for each dose:
Example:
(dose) x 1.5 (conversion number provided for syringe brand) = caliper mm
0.25u x 1.5 = 0.38mm
In addition to the videos, below are written instructions how to use the calipers once you know how many millimeters are in 1u on the syringe type you are using:
- Draw the insulin dose as you normally do (drawing a little excess) and flick out the bubbles.
- Slowly push the plunger in and expel insulin until you are close to but still in a little excess of the current dose.
- Turn the calipers on, make sure you have selected mm (the "mm" will be in the lower left corner of the screen), push the caliper head all the way down so the arms are together and then hit the "zero" button to zero them out.
- Move the caliper head in the opposite direction to "dial" in your mm setting that is equivalent to your dose. When the correct distance measure shows on the screen, tighten the screw down. Double check the number shown in the screen and make sure it hasn't changed (sometimes tightening the screw will cause the number to go up or down by .01). Once you have set the distance for a specific dose (e.g. on the Terumos, 1.52mm for 1u), then you do not need to change it unless you change the dose. If you change the dose, zero out the calipers again and then reset for the new measurement associated with your new dose.
- In order to use the calipers correctly, the bottom of the upper caliper arm should line up perfectly with the plastic rings around the syringes where the zero line would be (the plastic ring might be located differently in syringes other than Terumos and Monojects). It might be off just a tad in the photos below but hopefully you will get the idea. Then the top of the bottom arm of the caliper should line up flush with the top of the plunger. Again...the Terumo is way off in the photo but the Monoject is pretty close so you can imagine what the Terumo should look like.
- If you are using BD syringes, you will use the outside edges of the small arms measure the dose.
TERUMO SYRINGE (above)
MONOJECT SYRINGE (above)
- Be sure you do not confuse millimeters and dose!!! For example, 1.52mm is NOT 1.5u. You must calculate the millimeters equated with a particular dose following the instructions above.
- Please be sure and record the dose in the "U" column on the SS as "units". Please do not record the mm setting in the "U" column. We all measure a little differently and the syringes differ in barrel circumference, etc, so your mm measurement is likely different from mine; the important part is you are consistent with your measurements. A "mm" measurement in the "U" dose column tells us nothing about dose and providing good dosing suggestions becomes impossible (and unsafe). If you want to record the caliper measurement on your SS, please either make a separate column that distinctly labels it or, better yet, put it in the remarks section. It is really only to assist you, not anyone helping you.
- Remember that when you are using calipers, you do not need to worry about the unit marking lines. I usually double check and just make sure my dose measured with the calipers is in the vicinity of the correct unit marking. In other words, if the current dose is 1u and you measure it with the calipers but when you look at the syringe, the plunger is near 2u, there is something wrong.
If you have any questions or need any help, please be sure and ask. Many members are using calipers and can help or you can PM me.
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