What’s the secret to growing strong, healthy nails?

Growing your nails takes time. From age, to chronic illnesses, to even the time of year, lots of factors can impact the speed in which your nails grow.
Whether you’ve broken a nail and are trying to grow it back, or you have an underlying condition that’s causing brittle nails, unfortunately, there’s no surefire way to achieve rapid nail growth overnight.
However, there are steps you can take to strengthen your nails, which in turn promotes nail growth. We asked the experts to weigh in with a few dermatologist-approved tips to help you grow strong, healthy nails.
Healthy fingernails grow approximately three and a half millimeters every month, says Dr. Soraya Azzawi, MD, FAAD, a board-certified dermatologist and health sciences clinical instructor at UCLA.
Toenails grow slower than fingernails. On average, toenails grow around one and a half millimeters a month, says Dr. Chris Sayed, MD, a clinical professor at the University of North Carolina at Chapel Hill Department of Dermatology.
If you happen to lose a nail, you can expect it to take at least a few months to grow back. “A normal fingernail would take about six months to grow out, whereas a toenail would require [between] one to one and a half years,” Azzawi says.
It’s not unusual for nail growth to differ from person to person. One of the primary factors to influence nail growth is age, says Sayed. “Older adults have much lower nail growth [rates] than a young child,” he says.  
Hormones also play a role in determining how fast nails grow. For instance, “an estrogen and progesterone surge during pregnancy will lead to faster nail growth,” Azzawi notes.
Nails tend to grow faster on your dominant hand, Azzawi adds. Because you use it more, your dominant hand is more at risk for experiencing trauma. If you injure a nail, the body will flood the area with more blood and nutrients. This may potentially accelerate nail growth, according to Healthline.
The seasons can also impact nail growth. Nails usually grow faster during the warmer months, although the difference is quite subtle, says Sayed. 
It’s possible for immunocompromised individuals to experience inhibited nail growth, Azzawi says. Chronic conditions that can affect the growth and appearance of your nails include: psoriasis, endocarditis, lupus, kidney disease, thyroid disease and liver disease, per Healthline.
If you’re perfectly healthy and not immunocompromised or malnourished, “there’s not really anything somebody can do to make their nails grow physically faster,” Azzawi says. However, there are steps you can take to strengthen your nails, which will reduce the possibility of breakage, and make sure your nails are growing properly. 
Grooming your nails, and trimming them regularly, is an important part of nail health, per Healthline. To promote the growth of strong, healthy nails, Azzawi also suggests:
For individuals with brittle nails, biotin (vitamin B7) supplements may offer nail strengthening benefits, Azzawi says. Small clinical trials have shown biotin supplementation may improve the firmness, thickness and hardness of brittle nails.
If you’re considering taking biotin supplements to help strengthen brittle nails, always be sure to consult your doctor first, says Sayed.