“Brittle nails are a common sign of having an underactive thyroid (hypothyroidism) – where your thyroid gland under-produces hormones. It’s important an underactive thyroid is diagnosed as quickly as possible. This is usually done via a blood test.”
Red/ purple lines or clubbing
Heart disease could be the underlying cause.
“Generally, red or purple lines under your nails are due to an injury. But if you notice these and don’t recall injuring your nail, you might want to book a doctor’s appointment because these can be a symptom of heart disease.”
“Clubbing can also be a suggestion of heart disease, a major cause of death worldwide. This is where the nail curves over rounded fingertips or the ends of the toes, resulting in a bulbous appearance.”

White nails
If you notice ghostly nails, it’s important to get checked for liver disease.
“Named after the doctor who discovered the symptom, Terry’s nails is a nail condition where more than two-thirds of the nail bed turns white, with a red or pink strip remaining at the tip of the nail.”
“Terry’s nails are a classic indicator of liver disease. Other signs of the disease include fatigue, yellowing of the skin, and a loss of appetite.”
Small dents

Skin problems…
“Small dents or pits on the surface of the nails are common in people with skin disorders such as psoriasis, eczema, and alopecia areata – a specific type of hair loss.
“You’d expect other visible symptoms. For instance, psoriasis often leads to dry, scaly skin patches, while eczema results in dry, itchy, cracked, and sore skin. Alopecia areata is characterized by patchy hair loss.”
Horizontal ridges lines

Bad health…
“Deep lines or grooves across your fingernails are referred to as Beau’s lines. This temporary interruption in nail growth is typically triggered by a serious illness or infection. Some individuals developed Beau’s lines after experiencing COVID-19, for instance.
“If you notice Beau’s lines and are worried, I’d suggest scheduling an appointment with your GP to discuss your overall health.”