Choosing and Buying Needles

One of the more complicated parts of giving subq fluids to your cat is learning how to choose the right needles to use and finding where to purchase the needles from.

For most people giving subq fluids to their cat the needle of choice is the Terumo TW 19g x 1″ or 20g x 1″.

Needle Label Meanings

If you’re not familiar with needles the sentence I wrote just above this is probably confusing. That’s completely normal! So, before I go any further, I want to break down what those letters and numbers mean. Each of these things will be covered in detail so this is just a quick summary.

Terumo TW 19g x 1″ or 20g x 1″

TerumoThis is the brand/manufacturer of the needle
TWThis is the thickness of the needle wall. Needles come in RW, TW, and UTW, but wall thickness is partially determined by needle gauge. Wall thickness, combined with gauge, affects the outside size of the cannula/shaft of the needle.
19g and 20gg = gauge
Needle gauge refers to the size of the lumen, the hole in the needle. Gauge, combined with wall thickness, affects the outsize size of the cannula/shaft of the needle.
Gauge affects the rate of speed for fluid delivery. Smaller gauge = larger lumen = faster fluid delivery speed.
1″This is the total length of the needle, measured in inches

Anatomy of a Needle

basic anatomy
detailed anatomy

Needle Brands

An independent study in 2009 by the DDL laboratory in Minnesota compared the sharpness of different needles, and Terumo was the clear winner.

In 2014 the brand BD changed the tips of their needles to make them sharper. To my knowledge there have not been any repeat studies to compare the sharpness of the needles after that change.

Sharp needles matter because the sharper the needle is, the easier it will slide into a cat’s thick skin.

Typically your vet will stock Monoject needles so that might be the brand you start with. Monoject, as far as I can tell, uses a 3-bevel point. They also mention a “special bevel grind specifically for use in animals” but I could not find any explanation of what that means.

Bevel Type

The sharpened angular tip of the needle is the bevel. You’re not going to really have any option to choose your type of bevel, aside from picking the brand of needle itself, but it’s good to understand the different types because it can help you to understand needle sharpness.

The bevel is the combination of the different cutting edges of the needle. Most needles are a standard 3-bevel tip. This means there are 3 different cutting surfaces for the needle. BD created a 5-bevel tip needle in 2014. You can see there are 2 additional cutting edges. This changes the way the needle pierces the skin, making it more comfortable.

bevel type comparison

Wall Thickness

The thickness of the needle wall partially determines how big around the diameter of the cannula of the needle is.

Needle are available in three different wall types:

  • Regular wall (RW)
  • Thin wall (TW)
  • Ultra thin wall or extra thin wall (UTW or ETW)

This image should help:

Imagine you are staring into a needle from the tip. The white circle in the center is the lumen (the hole) in the needle. The colored part is the metal that makes up the cannula (the outside) of the needle. You can see that the thinner needle wall makes the cannula of the needle smaller even though the lumen of these needles is exactly the same size. Ideally you want the thinnest wall you can get for your needle.


The gauge of the needle is the size of the lumen (hole) on the inside. Gauge is mostly going to determine how fast or slow your fluids flow. Needle gauge goes backward from what you would normally expect. A large number for the gauge (e.g., 25) will have a much smaller lumen than a smaller gauge number (e.g., 18).

The paper clip in the image is to provide a reference for how thick the outside of the needle is.

Although gauge is a measure of the diameter of the lumen of the needle, it has an effect on the total cannula diameter too. The image above is a fairly good representation of gauge even though it does not show the actual hole size.To get an idea of how the gauge of the needle affects the speed of giving fluids, check out this comparison chart.


Needles come in a variety of lengths. The available length is generally determined by the brand and gauge of the needle you choose. Most people will use either 3/4″ or 1″ needles with their cats.

Some needle gauge and wall combinations are only available in special needle styles.

Overall Style

There are essentially two styles of needle you can use for subq fluids; regular hypodermic needle or winged infusion set (butterfly needle).

Most people use a simple hypodermic needle for fluids, but there are a couple of reasons to consider using a butterfly needle.

I typically use a butterfly needle because my needle of choice is the Terumo UTW 21g 3/4″ and that combination of features is only available in a butterfly needle. I use the syringe method for giving fluids to my own cats, and I like the extra extension tubing that the butterfly needle is connected to. I really like the butterfly wings as well. They make gripping the needle just a little bit easier.

Butterfly needles are more expensive than a regular hypodermic needle. Regular hypodermic needles can usually be purchased for less than $0.10 (USD) each and butterfly needles are closer to $0.60 (USD) each.

Where and How to Buy

There are many options for where to purchase from, though depending on where you live there may be some restrictions on that. Tanya’s Comprehensive Guide to Feline Chronic Kidney Disease has some great ideas on where/how to purchase needles (and other supplies too).

If you are in the United States you can generally purchase needles without a prescription. There are only 4 or 5 states where a prescription is required.

In an “emergency” situation if you need a small amount of needles you may be able to get them from any pharmacy without a prescription (unless you live in a prescription-required state). The pharmacist will ask what you need the needles for, and they’re likely to limit you to 10 needles or less for these purchases.

I do not recommend purchasing needles from Amazon or from online auction sites such as eBay. Amazon has major problems with counterfeit products and, although needles are unlikely to be counterfeited due to low profit margins, I still would not risk it. I would not risk eBay because I don’t trust that the products have not been tampered with. I prefer to purchase all needles and other medical supplies from licensed pharmacy or medical supply distributors.