What actually differs between the two
The two ThunderBites products do not share the same calming formula. The regular Calming Chew (formerly ThunderWunders, 60 count) has, per chew, chamomile 50 mg, thiamine (vitamin B1) 25 mg, passion flower 25 mg, ginger 25 mg, L-tryptophan 15 mg and melatonin 10 mcg, and is given 30 minutes before a stressful situation. Calm + Probiotic (90 count) is a daily chew with, per chew, ashwagandha 150 mg, L-theanine 30 mg, L-tryptophan 15 mg, chamomile 10 mg, ginger 25 mg, vitamin B1 0.5 mg and melatonin 1.5 mg.
On top of that, Calm + Probiotic adds a probiotic blend (3 billion CFU per chew; 6 billion per 2 chews) along with inulin (prebiotic) and EpiCor (postbiotic). That blend is aimed at digestive and gut health, not at calming. So the real questions are how you'll use it (as-needed before events vs every day), how much melatonin you want your dog to get (10 mcg vs 1.5 mg per chew), and whether your dog also needs gut support.
| Feature | Regular calming chew | Calm + Probiotic |
|---|---|---|
| Calming ingredients | Chamomile, thiamine, passion flower, ginger, L-tryptophan, melatonin 10 mcg per chew | Ashwagandha, L-theanine, L-tryptophan, chamomile, ginger, B1, melatonin 1.5 mg per chew |
| Gut-health blend | None | Probiotic (3B CFU per chew), prebiotic and postbiotic |
| Best for | As-needed calming, 30 minutes before events | Daily calming support plus digestive issues |
| Age | 12 weeks and older | 12 weeks and older |
Original10 mcg melatonin, 15 mg L-tryptophan, 50 mg chamomile, 25 mg thiamine per chew
- Dose by weight
- Up to 26 lb: 1 · 27–50 lb: 2 · 51–99 lb: 4 · 100+ lb: 6
- How to use
- As needed, 30 min before the stressor
HempSame actives as Original plus 75 mg hemp seed oil and 75 mg hemp seed powder (not CBD)
- Dose by weight
- Up to 26 lb: 1 · 27–50 lb: 2 · 51–99 lb: 4 · 100+ lb: 6
- How to use
- As needed, 30 min before the stressor
Calm + Probiotic1.5 mg melatonin, 30 mg L-theanine, 150 mg ashwagandha, 3 billion CFU per chew
- Dose by weight
- Up to 25 lb: 1 · 26–50 lb: 2 · 51–75 lb: 3 · 76–100 lb: 4
- How to use
- Daily, every day
From ThunderWorks labels (actives listed per 2 chews, shown here per chew). Ask your vet before giving Calm + Probiotic to small dogs, puppies, pregnant dogs or dogs on medication.
Regular vs Hemp
The Hemp version keeps the same 6 actives as the regular chew, with the same dosing chart and 30-minute timing. It adds two things per 2 chews: 150 mg hemp seed oil and 150 mg hemp seed powder (75 mg of each per chew). Neither is CBD. Hemp seed has essentially no cannabidiol, so do not expect a CBD effect. See our hemp seed vs CBD guide.
The decision: probiotic or regular
The calming sides differ, so start with use: daily support points to Calm + Probiotic, occasional events to the regular chew. Then look at your dog's gut. Use this framework.
Choose Calm + Probiotic if your dog:
- Has loose stools, frequent gas, or a stomach that upsets easily during stress
- Is prone to soft stools around travel, boarding or vet visits
- Is coming off a diet change, or you want ongoing digestive support alongside calming
Choose the regular calming chew if your dog:
- Has normal, consistent digestion and no history of tummy trouble
- Already gets a separate probiotic you are happy with
- Only needs calming support, with no gut concern to solve
Calm + Probiotic is not just the regular chew plus probiotics: it adds ashwagandha and L-theanine and has 150 times more melatonin per chew (1.5 mg vs 10 mcg). That melatonin dose is meaningful, so ask your vet first for small dogs, puppies, pregnant dogs or dogs on medication. If your dog is on antibiotics or being treated for a specific condition, ask your veterinarian before starting a probiotic.
Related: -ThunderBites chews for small breed dogs with anxiety
Do probiotics make a dog calmer?
You may have read that a healthy gut supports a calmer mind through the "gut-brain axis." In dogs, this is an active but early area of research. A 2024 review in Veterinary Medicine International concluded that while the gut-brain axis is plausible and worth studying, there is still a shortage of solid canine behavior research, and probiotics should not be thought of as a calming treatment on their own. A few small studies have shown specific probiotic strains nudging anxiety measures, but the evidence is not strong enough to promise a behavior change.
The honest takeaway: the calming ingredients are what you are relying on for calming, and the probiotic blend is a gut-health add-on. If it happens to help behavior indirectly by settling the stomach, treat that as a bonus, not the reason to buy.
Related: -Are ThunderBites dog calming chews too hard for small breeds
Dosing and getting started
The two versions use different weight charts. Calm + Probiotic: dogs up to 25 lbs get 1 chew daily, 26 to 50 lbs get 2, 51 to 75 lbs get 3, and 76 to 100 lbs get 4, so a 90-count jar lasts 22 to 90 days. Regular (and Hemp): up to 26 lbs 1 chew, 27 to 50 lbs 2, 51 to 99 lbs 4, 100 lbs and up 6, given 30 minutes before the stressful situation and no more than double in 12 hours; a 60-count jar covers 10 to 60 doses. All three products are intended for dogs 12 weeks and older.
With Calm + Probiotic, give the chew at the same time each day so it becomes part of a routine, and store the container sealed in a cool, dry place. Calming ingredients like L-theanine and ashwagandha are generally used daily rather than as a one-off; if you chose the probiotic version for digestion, gut support also works best with consistent daily use. Watch for any loose stools when introducing a new supplement and check with your vet if anything seems off.
Once you know whether your dog needs the gut-health blend, the choice is simple. Pick the version that matches your dog and keep the routine steady.