6 Month Old Baby Fussy All Of The Sudden? (I Know 6 Reasons Why)

It’s normal for 6-month-old babies to get fussier around this age, and keep in mind that it’s totally alright and nothing to worry about. There are many reasons why 6-month-old babies are extra crankier, and that can be because: they’re teething, going through a growth spurt, or adjusting to eating solids. They can also be irritable if they’re in the phase of achieving a milestone like crawling or sitting. Also, look out for illnesses like cold or flu, which can also make babies very uncomfortable. Another primary reason why 6-month-old babies are crankier is that some babies may go through a sleep regression, including multiple awakenings at night and sleeping for more extended periods during the day.

Hi, dear concerned parent,

You have completed your three trimesters of pregnancy and the fourth trimester- your baby’s first 3 months are also done and dusted. You finally get the hang of things and have found your parent groove, but then bam! Your baby has suddenly become unusually fussy and cranky.

Isn’t it after the fourth trimester that we finally know what we’re doing?

The endless hours of no sleep and changing diapers every 3 hours, and feeding our little one every 2 hours makes us realize that, well, if we can take care of a baby, we can probably pretty much do anything.

We’re so careful with everything we do, whether it is bathing our little ones or changing clothes, we make sure that they’re safe and protected, and when this little bundle of joy starts getting fussy out of nowhere, we may start questioning everything we’ve been doing.

It’s pretty expected for parents to panic when our little kiddo, who always smiled first thing in the morning, and laughed every time we sneezed, has suddenly forgotten to smile and is always fussier and cranky and doesn’t like anything anymore.

But remember that a fussy baby is normal and expected. It’s their only way of communication. If they could use words, they surely would and tell you what’s troubling them, but being fussy or being irritated is their only way, for now, to tell you that something’s not right for them.

Here are some common reasons why your little one is extra fussy at 6 months of age.

6 reasons why your 6-month-old baby is fussy

📌 Note: I’m going to list some of the general reasons that make most babies fussy, but if you think your baby’s showing severe symptoms, follow your gut and consult your pediatrician immediately.

1. Teething

A teething 6-month infant boy is biting on 2 of his fingers and drooling.

Teething is one of the most common reasons babies can be very fussy. However, when teething starts for every baby can be completely different, so don’t compare your child with anyone else’s.

Babies can start teething anytime from 4 months till even after 12 months of age, but most babies, generally, start teething at the age of 6 months.

For my son, his bottom tiny two pearly whites, the central incisors, made a debut just before his half-birthday, and I remember those days very well because he wouldn’t sleep at all.

During the day, I would try all different things to calm his gums like teethers, cold silicone teethers, teething biscuits, and little sips of cold water to help him soothe, but at night, he wouldn’t sleep at a stretch and would wake up multiple times crying and not even wanting to feed.

So, teething can be the reason why your baby is fussy. Look out for any cuts in their gums, or swollen spots on gums, excessive drooling, and your baby trying to put everything in their mouth.

You can also try offering them popsicles made from breastmilk to help them soothe their gums.

2. Growth spurt

Babies grow rapidly in the first year of their life, and much of that will happen during their growth spurts. During growth spurts, there tends to be an increase in their height and weight.

You might notice your baby becoming fussier and even hungrier. So, it’s definitely not your imagination when your 6-month-old baby can’t suddenly fit into their onesies.

Breastfed babies might want to be fed more than usual, and the 3-4 hours gap between every feeding is thrown out the window. Formula-fed babies might want bigger bottles too.

So, now is the perfect time to introduce a variety of mashed foods for your baby. You can even try baby-led weaning for your little one to be more independent and in control.

They might not sleep at all in the night and might sleep like a log during the day.

3. Starting solids

Starting solids can take the pressure of exclusively being dependent on milk, but this also means that their body is now trying to cope with all the new types of foods entering the body.

Babies are constantly developing mentally and physically, so their digestive system, which was only fed milk until now, is supposed to adjust to all the green and orange stuff you’re feeding to your baby.

So, the chances are that your baby might feel constipated, experience stomach aches, become gassy, bloated, or even have diarrhea. These symptoms can make them feel very uncomfortable and result in them being crankier and fussier.

Try offering more water along with solids to help with constipation.

Look out for foods that make them gassy or constipated.

4. Sleep regression

Did you introduce a bedtime routine or a sleep routine, and your little one has been cooperating till now? Well, it might end now.

There are no straightforward reasons why some babies experience sleep regression at the age of 6 months.

A tired mom is helping her 6-month-old infant boy try to sleep, he's going through a sleep regression.

Still, it’s believed that because they develop so quickly and at an uneven rate, they might experience sleep regression.

While not all babies go through this period, some babies do.

As they mentally develop, they become more aware of their surroundings, become more sensitive to sounds, or have separation anxiety, resulting in poor sleep at night.

So, babies who used to sleep like a baby till now might not do so. They might not sleep at a stretch at night and will sleep during the day.

Sticking to your bedtime routine and sleep training will help them go back to sleep throughout the night.

Try to minimize any distractions at night; a white noise machine may help.

Put in blackout curtains too in their room, so that light and maybe sound to an extent, is blocked out.

5. Achieving milestones

A baby’s mind and body are developing and unfolding at a quicker rate. Your child, who used to only sit on your lap till now, has started sitting on his own.

During these phases, it’s normal for children to roll over both sides or crawl or sit, making them fussier and crabby. But this doesn’t mean you pick them up every time they become cranky.

Let babies learn and do it on their own under your supervision. This is also the best time to baby-proof your house so that the baby doesn’t crawl somewhere or get his hands on something.

6. Baby cold or flu

Developing allergies is quite common, especially after introducing solids.

An unwell infant boy is sleeping as mom check his temperature for a possible fever

Make sure to make a note when your little one is fussier than usual after eating his food. Chances are, they might be allergic to a particular food.

Consult your pediatrician if this happens.

Also, along with allergies, your baby might be coming down with a cold. It’s flu season throughout the year with kids. So you never know when they will fall sick.

My little one got his first cold when he was 6 months old, and it ached my heart to see him struggle with a stuffy nose, congestion, and cough.

There’s not much you can do when your baby has cold other than giving them lots of steam baths, offering warm fluids, and providing them with plenty of rest and love.

If you’re breastfeeding, continue to do so because the antibodies in your milk can help them fight the virus.


How much water should I offer my 6-month-old baby?

You can offer up to 2 to 8 ounces of water in a day.

Let them take sips from their cup throughout the day, but make sure you offer plenty of breast milk or formula.

What finger foods can I offer my 6-month-old baby?

You can offer raw sticks of cucumber, cooked sticks of carrots, baby sweet corn, soft cooked florets of cauliflower or broccoli.

Is a 3-hour nap too long for my 6-month-old baby?

It’s normal for babies at 6 months to sleep 2-3 hours during the day, but make sure not to let them sleep for more than 2 hours late in the day, as they might not sleep long during the night.


Getting worried or panicked because your baby behaves out of their character is quite typical and expected for new parents. Still, babies being fussier and crankier at unusual times is typical and expected.

Having said this, if you notice your baby having symptoms like rashes, hives, or swollen lips, rush him to the emergency. Also, consult your pediatrician if you think something isn’t right with your baby.

But more often than not, the above reasons are why babies are fussier at 6 months of age.

Meanwhile, give your little ones much love, cuddles, and kisses.

Happy parenting!

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Located in India and a mother to a joyfully mischievous son, Kelin is the wife of the world’s most patient man and a busy homemaker. When she’s not busy cooking and running after her kid,  you can find her in a corner reading, or penning down words on her laptop. She believes the world will always try to instil ‘mom guilt’ in new mothers, but she goes by the maxim ‘a mother knows best'.

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