Refusal to eat / Force-feeding
Disclaimer: I am only writing about my own experiences at this site. Please don't ask me for advises if your beardie seems sick. I can't - and won't - take that responsibility - if you are worried about your dragon - consult a veterinarian, immediately!
Change of behavior
If your lizard changes its behavior you should always find out why. I personally take a fecal sample, from each of my lizards, to the vet at least a couple of times a year to check if they have parasites. Parasites are a very common reason that they stop eating. If it is an adult bearded dragon it might want to brumate - but still - you need to check that it is healthy anyway.
If a free of parasites and healthy fully-grown bearded dragon doesn't eat for a week, it is not dangerous - or unusual and you probably don't have to worry. They have their periods when they eat less, or not at all (breeding season for example). But if your dragon doesn't eat for 10 days or so you should find out why.
Babies that stop eating
If it is a baby/juvenile dragon that stops eating it is much more alarming. It is not unusual that a baby doesn't eat much the first week after you purchased it, but as long as it eats a little you probably don't have to worry. The baby doesn't have to be sick. It probably just need some time to adjust to its new home. Leave it alone as much as possible and keep offering food. The little dragon will probably start eating well again.
When a baby bearded dragon stops eating it can be many reasons. Unfortunately it is impossible to mention every reason here. You have to use your common sense and try to figure out why it stopped - and consult a veterinarian. Below you find some of the reasons.
The dragon can have parasites or be sick. Always check with a vet if they stop eating and you don't know why. This is especially important with baby dragons.
The basking spot shall be in the high 90's to 100 degrees for an adult dragon, babies shall have it a little warmer. If it is too cold the dragon can't digest its food and it won't eat. If the rest of the cage is too hot - that isn't good either. The ambient temp shall be at the lower 80's.
Do you handle your dragon too much? If you recently purchased it, it can be very stressful and it stops to eat because of that.
Is the cage placed in a busy area of your home, where a lot of people pass by? If you think that the environment is too stressful - move the cage to a calmer part of the room and/or cover the sides (if you have a glass cage) so that only the front is open.
Do you have other pets that your dragon can see? Many dragons find cats, birds and dogs etc. very frightening.
Do you have kids that are constantly watching/touching the dragon? Tell your kids to leave the lizard alone…
Do you play loud music? That can be stressful. Turn it off.
Is the cage located near a window so the lizard can see birds etc. outside? Move the cage or try to prevent the sight out the window.
Is the cage placed directly on the floor? Most dragons feel threatened if they are "too far down" since most natural enemies comes from above.
Do you have a fan in the ceiling? Turn it off. Many dragons believes it is a attacking bird…
Dominant cage mate
If your dragon is housed with a dominant dragon it can stop eating. If you notice that the dominant dragon pushes the submissive dragon aside - you have to separate them. The signs of domination might not be crystal clear to you, so you have to be observant.
"Wrong" feeding technique
You can also look into the technique you use to feed your baby dragon. Try another technique and see if that helps (hand-feed, feed in separate cage, let him chase the crickets' etc, try something different). See when, and if, the baby seems frightened - and if so - when? Change the thing that is scaring him. On the other hand - try to be consequent, don't change the way you feed him all the time. If you do, the baby don't know what is going on and that is scary too…
Crickets are too big
Small dragons can be afraid of big crickets. You shall never feed crickets bigger than the space between your dragons' eyes (it can in fact be lethal). Change to smaller crickets - and offer just 2-3 crickets at the same time. Too many crickets in a cage can be "too much" for a little dragon.
There can be a hundred reasons… try to use your common sense and "feel" what might be wrong. Often you get the answer if you just "listen" and watch your dragons' behavior closely.
Don't try "too hard"
I know how frustrating it is when a dragon doesn't eat and you have no idea why. But you have to try to relax and don't try "too hard". If you try too hard and keep trying all the time it is very stressful for the lizard - and they stop eating because of that. Try to leave the dragon alone as much as possible.
Fluids are very important
If the baby dragon doesn't eat - you have to make sure it gets fluids. That is very important. Unfortunately is dehydration a very common cause of death in baby dragon. Read more under "Water"
This is how I do
Note! This is how I do - I am not an expert - so please consult a veterinarian as well. I can't enough point out how important that is!
Never ever force-feed your dragon crickets or worms - the dragon can get scared and connect the crickets with discomfort.
Chicken baby-food mixture
When a baby bearded dragon hasn't eaten for 3-4 days I try to "break that bad habit". Sometimes baby dragons actually get in their head that crickets are dangerous for some reason and stops to eat, without any "real" reason. When a baby hasn't eaten for 3 days I stop offering crickets for a week. Instead make a mixture of "baby chicken food" (for the smallest human babies) a little bit of calcium powder, vitamins and water and offer this mixture via a syringe (without the needle of course!) to the baby dragon.
Giving the baby the mixture
I put the baby dragon in my hand and drip a little mixture at the tip of the babies' nose and usually they start to lick when they taste it. If they don't start licking, try to put the tip of the syringe in the corner of the babies' mouth and gently put some mixture in there. Usually there is no need to force the mixture into the dragons' mouth. If you have to force-feed your baby - be VERY careful and don't give too much mixture each time. Make sure the baby has plenty of time to swallow.
Make a fresh mixture every day, never keep it over night and always serve it room temperature.
If you feed your dragon this way make sure it is ONLY temporarily. This is not a perfect mixture for a dragon. This is just to get some nutrition and fluid in them and to make them start eating by themselves. Always consult a veterinarian!
When you have done this for a week you can try to offer your baby fruitflies. Or very-very small crickets.
Again - please remember that I am NO expert when it comes to this. Don't experiment by yourself. If you are worried you shall contact a veterinarian. Your beardie might be sick and in desperate need of treatment. It is always better to be safe than sorry and contact the vet "one time to much" rather than to "wait and see what happens".
Another nutritious mixture:
Finely pulped banana (stimulating)
Yogurt (for the stomach)
Egg Yolk (protein)
Water (to thin down a little)
Crushed crickets (nutritious)
Maybe some Fruitflies (nutritious)
Some baby chicken food (nutritious)
It is hard to tell how much you shall mix of everything. I really don't know, but I guess half a teaspoon of everything will be ok. Make a new mixture every day. It is very important that it is fresh. Wait to feed this until everything has room temperature.
It was absolutely disgusting to crush the crickets. But for my Teo I do anything. I put the crickets in a small plastic bag and took the heaviest book I have and then - BAM! Yuk! Then I had to scrape out the entrails of the cricket. The shell of a cricket is too hard to digest for a beardie that hasn't eaten for a while.