Vitamin D deficiency typically goes unnoticed until you end up sick and realize you have a deficiency. Another challenge is that it takes time, usually at least several weeks, to raise vitamin D levels. As a result, a few days of taking supplements is not going to cut it. This is true especially if you have a serious deficiency challenge to overcome or already have the flu.

Below are 5 signs that vitamin D is likely a problem and potentially a serious deficiency that needs to be addressed immediately.

1. Chronic Pain

“It’s often subtle, but some experience aches and pains in the bones, known as osteomalacia,” Holick says. Those who are diagnosed with arthritis or fibromyalgia may actually be shy of enough vitamin D, which can cause joints and muscles to ache, too.

If your discomfort lasts for several weeks, ask your doctor if a vitamin D deficiency could be the cause—and if your treatment program should include the vitamin. Also worth noting: adequate vitamin D can prevent post-workout pain and increase the speed of muscle recovery,

2. Muscle Weakness

Here’s a shocker most folks don’t realize: most muscle weakness issues are low vitamin D related. The National Institutes of Health reports that a person suffering from a vitamin D deficiency will have trouble with proper muscle function.

Muscle strength isn’t just a matter of pumping iron. While having a vitamin D deficiency can leave you feeling overly exhausted, even when you’re able to get enough shut-eye, proper vitamin D intake helps you maintain power in every fiber of your being, whether you’re young or old.

Harvard researchers have linked vitamin D supplementation with increased muscle control, resulting in 20% fewer falls among adults around 60 years old. Promising news: Within just six months of supplementation, D-linked muscle weakness can be eliminated, according to a Western Journal of Medicine study.

3. Psoriasis

This extremely common skin issue is an autoimmune disorder that many don’t realize can be vitamin D related. This nutrient plays an important role in the treatment of psoriasis. Psoriasis gets worse over time and spreads, so even if you only have a little spot on your elbow or knee, get your vitamin D levels checked and be sure to take a daily dose of fermented cod liver oil.

4. Constant Fatigue

Vitamin D is necessary for the body to produce energy. If you are constantly tired or must rely heavily on that morning cup of Joe to get going in the morning, best to play it safe and get your levels checked.

5. Depression

A depression diagnosis is often actually linked to a shortage of vitamin D. While the jury is still out about why, the Vitamin D Council says that the mineral may work in the same brain areas as those that affect mood.

No, it’s not all in your head! Feelings of hopelessness can be related to nutritional D deficiency. The Vitamin D Council reports that vitamin D is critical for the brain to produce the happy hormone serotonin. Some folks only suffer from depression during winter months, known as Seasonal Affective Disorder (SAD). This condition is caused by lack of sun exposure and vitamin D.