(This story originally appeared on Grandparents.com)

Twice a week, you babysit your grandson, feed him lunch and take him to the park. So naturally, you’re going to notice a thing or two. But whether to interfere or not is tricky for grandparents.

“In the long run, it’s best for the kids and family if the parents do the parenting — even if a grandparent disagrees with the approach,” explained Carl Grody, a family counselor in Worthington, Ohio.

While as a grandparent you may feel you have valuable child-rearing experience to offer, sharing this wisdom can backfire if the parent senses criticism. But there are a few times when it makes sense for a grandparent to step in:

1. Rudeness
“As in all relationships, you’re entitled to set boundaries for the way people treat you,” said Grody. If your grandchild is rude to you or to others, you should speak up. You could say “It’s not OK to talk to me like that.” However, leave any discipline to the parents. And don’t insist the parent deal with the issue in front of the child or you risk undermining the parent’s authority. Instead, tell the parents about your grandchild’s behavior when the child is not in the room and give details.

2. Developmental delays
Sometimes, parents are too close to their children to notice when there could be something wrong. Grandparents have raised children before, so they often know what to look for when it comes to a child’s development. If you notice your grandchild has a speech delay, motor problem or difficulty with a social skill, it is important that you speak up. The problem could worsen if left unchecked, and early intervention is often critical to getting kids back on track, said Amy Morin, a psychotherapist in Lincoln, Maine.

3. Safety
There is no question about this one. Definitely butt in when it comes to your grandkids being safe — but you can probably only do this a limited number of times. Reminding your grandchild to wear his bike helmet is fine, but badgering the kid’s parent about it is not. In your own home, of course, you are free to set the rules and enforce them.

“It’s fine to say ‘Everyone wears a helmet when they ride a bike at Granny’s,’” said Morin. And if you’re concerned about a larger safety issue, such as your grandchild crossing the street alone, talk to your adult children when your grandkids are not in the room. That way, you can have a more open conversation.

4. Nutrition
You want your grandchild to eat well, but wisdom says tread lightly when it comes to food. You can certainly serve green beans and carrots at your own house, but you can’t dictate the menu elsewhere.

“Be sure to give a positive spin whenever you can — and avoid backhanded compliments,” said Grody. For example, if you see that Brussels sprouts are being served, say “This looks good” rather than “Well, I see we finally have something green.”

And if you’re worried about your grandchild’s eating habits or the snacks he is eating, it is perfectly fine to talk to him about healthy choices and give suggestions, but don’t undermine the parents.

5. The big stuff
Without question, you should instantly step in and talk to the parents if you notice any of the following: Physical or sexual abuse, true neglect, substance abuse by the parent or a mental health issue and imminent harm to the grandchild.

Keeping your grandchild safe is your top priority. If the child is in danger, consider contacting your local police department or your local Child Protective Services department.