Unfortunately, the Veterinary Medicines Directorate contacted me to tell me it was against the law to advertise this wormer since it was classed as ‘Prescription Only Medicine – Veterinarian, Pharmacist, Suitably Qualified Person (POM-VPS)’. and that ‘Products classed as POM-VPS can only be advertise in publications aimed at professional bodies and not to the general public’.
I was surprised they considered this page as advertising so I spoke to them and they advised me that I should not use the product’s brand name but could say ‘A product containing Flubendazole‘. As a result, I have removed the product name.
Before using medication to worm your chickens, it is best to check they need worming first by using a Worm Count Kit like this one. This is a simple test where a sample is sent off by post and the results are returned to you (usually by email) and will advise you whether or not you should worm your chickens.
In the United Kingdom, a product containing the anthelmintic (wormer) Flubendazole is currently the only licensed in feed product available for chickens. It is very effective at killing worms and their eggs. Worms can cause a huge amount of damage to chickens and cause many health problems. As a rule of thumb, if I have a sick bird, the first thing I consider is whether or not she was wormed recently before exploring other avenues because so many signs of illness can be as a result of worms.

The Direct Life Cycle
Worms lay thousands of eggs in a day that are not always visible in droppings. Eggs then either get picked up by birds scratching around the floor, eating from the ground or in their litter when housed (i.e. picked up directly) or are eaten by earthworms or other ‘hosts’ and passed on to our birds when they themselves get eaten (i.e. indirectly picked up).
These two routes of infection are called the ‘Direct Life-cycle’ and the ‘Indirect Life-cycle’ and can be understood better from the diagrams show that are kindly supplied by Elanco (formerly Janssen Animal Health) where two examples of direct infection and one indirect are shown.

The Indirect Cycle
Worm eggs are destroyed by heat, drought, a hard frost and UV from direct sunlight. For this last reason, I keep grass short in runs over the hotter summer months where my hens graze so that worm eggs can be destroyed. Over the colder winter months or below 10 degrees Centigrade. Worm eggs cannot mature and therefore cannot become infectious so I test my hens with a worm count kit and worm if necessary in the Autumn as the temperature starts to drop and in the Spring when worms become active again.
This product containing Flubendazole that I’m not allowed to name is very effective and after the recommended 7 day treatment, chickens are free of worms and eggs. One thing to remember is that the thousands of eggs deposited via droppings (or coughed up in the case of Gape Worm) are still present in the environment so if the worm infestation is bad, you will need to repeat treatment after 3 weeks to break the cycle before the newly acquired worms (picked up from the eggs) have a chance to mature and lay eggs themselves.
The withdrawal period stated on the tub is nil for eggs from laying hens. This means that you can continue to eat eggs whilst your chickens are being wormed. I’m sure you won’t be eating your hens but they must not be slaughtered for human consumption during treatment. Treated birds may be slaughtered only after 7 days from the last treatment.
Where to buy
If you have a small flock, there is a 60g pack sufficient to treat around 20 large chickens. This comes with a handy little measuring scoop so that you can get the quantity right. One 6 g scoop treats 2 kg of food for chickens. This is the simplest way to worm and if you mix it as I suggest above with a little oil, you can be sure your chooks are getting the required amount. There is also a 240g tub or gamekeeper pack which is more suited to 50 birds or more and lasts longer.
Because of the tight regulations and a license that sellers need to hold (costing over £600 I was told by one company), both of these products are becoming harder and harder to buy. I bought a 60g tub in 1998 and paid £12.50. A year ago I bought another one and it was £70! Serious money.
The product containing Flubendazole can also be purchased pre-mixed in layers pellets on websites such as Amazon in 5 or 20Kg bags which is handy if you don’t want to mix it yourself.
I haven’t seen many places selling this product containing Flubendazole online and vets don’t usually stock it unless they specialise in poultry. The ‘regulations’ are pushing people to go to their vets or other suitably qualified people yet in fact if you chat to chicken keepers, they are being offered offer other large animal wormers containing Ivermectin instead that are often bought in large packs for use on farm animals. These haven’t been tested on chickens so you end up with vets advising anything from a 7 to 30 day withdrawal periods for eggs (depending on the view of the vet of what will be ‘safe’) and although this is perfectly legal, my personal opinion is that this is wrong when there is a tested product available.
How I mix this product containing Flubendazole

Adding the ‘paste’ to the layers pellets before mixing well
If you but the pack or tub then it will come as a powder that must be mixed with your chickens feed. In order to get this to stick to my layers pellets, I mix it in a small tub with a little Olive or Cod Liver Oil. The ‘paste’ that this makes can then be poured over the right amount of (weighed) pellets in a bucket and mixed well. It sticks to the pellets and won’t fall to the bottom of the bucket like I suspect some of the powder would without the oil.
Remember to wear disposable gloves for safety (yes I know we forgot in the photos!) and follow the ‘operator warnings’ given by the manufacturers below at the end of this page. Remember to dispose of empty containers in the domestic refuse. Used containers should not be recycled.
Pre-mixed layers pellets of course are easier and layers feed lasts for around 6-8 months before starting to spoil so you can use it for further treatments during this time.
How often do I worm my Chickens
As you will see from my routine list of jobs and from what I said above, I check my chickens for worms using a worm count kit twice per year as a preventative measure. Following the results, I worm if necessary but I also worm new birds that we add to our flock or if I become suspicious of worms / ill thrift.
I rotate the runs my birds use so there is no build up of worms. I would suggest you check for worms every 3 months if your birds are on the same ground continuously.
In between times, I sometimes use Verm-X and Apple Cider Vinegar to help keep worm numbers down as well as keeping the grass short in the summer months to allow UV from the sun to kill worm eggs.
You can read more about worms on my worming chickens page
I’ve just found what looks like worms in the bottom of the coop. They was only in one dropping and I’ve not seen anymore in any other dropping. They didn’t wriggle, just looked dead. Do I need to worm my 3 chickens?
Yes, if you see worms in the poo (live or dead) it’s a safe bet they need worming.
Hi,
We have just got our first 3 brown hens and have come across your wonderfully informative website. The hens came from the flock ranging in the field belonging to our local feed supplier and are just over 1 year old. It is unlikely that they would have had any innoculations, so I was wondering if they should be taken to the vet to have jabs or whether using Flubenvet would be better. All 3 look in good health and settled in very quickly. One is producing 1 egg every other day so far – golf balls have been deployed! Many thanks.
Vaccinations need to be done as chicks so it’s too late now – but don’t worry, most chickens aren’t vaccinated. Flubenvet is a wormer (in the UK) and should be used periodically to control worms. Other countries use different wormers so you would need to enquire locally and find out what is being used.
One of my pekins is occasionally stretching her neck slightly and opening and closing her beak – maybe gapeworm? She’s not making any gasping sounds and seems perfectly healthy. I haven’t wormed them yet – they are in a mainly covered run and are about 10 or 11 months old – so I have decided to give them Marriages layer pellets premixed with Flubenvet and then repeat within the prepatent period for gapeworm which is 18-20 days I think. I use Nettex sanitising powder in the coop and run so hopefully that should kill any worm eggs too. Does that all sound sensible?
2 weeks ago I put 3 silkies in with the pekins – they are apparently 20 weeks old though I suspect one is a younger as she is smaller and her feathers seem less mature than the others. I was told they had been wormed though I don’t know when that was. Will it be ok for them to have the Flubenvet layer pellets at the same times as the pekins even if they were wormed fairly recently? I don’t want to overdo it if 3 lots with maybe only 2/3 weeks between each treatment is too much for them! What do you think please? And would some live yoghurt for a few days afterwards be a good idea?
Loving keeping chickens but only got my first girls last April and there’s a lot to learn!
Thanks for this great website.
Yes, it sounds like a plan. Many problems go away after worming, it’s the first thing to check. Yes, a repeat treatment for the Silkies is unlikely to cause them any problems.
My chicken has become poorly whilst being wormed ?
It could be coincidence but it is possible that she was carrying a heavy worm burden. When the worms are killed, they release toxins which can kill a chicken.
Thank you so much for your helpful article. I feel I have a much clearer understanding of worms and how best care to care for my hen. 🙂